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gh-149816: Fix SNI callback callable race#150018

Merged
encukou merged 12 commits into
python:mainfrom
kiri11:ssl-rc-ft-49
May 19, 2026
Merged

gh-149816: Fix SNI callback callable race#150018
encukou merged 12 commits into
python:mainfrom
kiri11:ssl-rc-ft-49

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@kiri11

@kiri11 kiri11 commented May 18, 2026 •
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Problem

Fix a use-after-free race in the SSL SNI callback on free-threaded builds. When sni_callback is replaced or cleared on one thread while another thread is mid-handshake, the old callback object could be freed before the handshake thread finishes calling it.

  • Reader side (_servername_callback): acquire sslctx's critical section, snapshot the callback with Py_XNewRef into a local, then release. The local strong reference keeps the callable alive for the duration of the call.
  • Setter side (sni_callback_set): already holds the same critical section via @critical_section clinic annotation. Uses Py_XSETREF to swap the pointer and decref the old callback atomically. The OpenSSL callback registration is set after the pointer is stored, so a concurrent handshake always finds a valid callable.
  • Setter clearing (sni_callback = None): unregisters the OpenSSL callback first, then clears the Python reference. Serialized against the reader by the same critical section.

Testing

Adds a free-threading stress test that spawns handshake workers and a callback-toggling thread concurrently.

Plus manually tested on MacOS.

Before

% ./python.exe -m test test_ssl -m test_sni_callback_race
Raised RLIMIT_NOFILE: 256 -> 1024
Using random seed: 2655205590
0:00:00 load avg: 4.31 Run 1 test sequentially in a single process
0:00:00 load avg: 4.31 [1/1] test_ssl
==================
WARNING: ThreadSanitizer: data race (pid=68672)
  Write of size 8 at 0x000126f10588 by thread T29:
    #0 _ssl__SSLContext_sni_callback_set_impl _ssl.c:5304 (_ssl.cpython-316t-darwin.so:arm64+0xe5f0)
    #1 _ssl__SSLContext_sni_callback_set _ssl.c.h:2266 (_ssl.cpython-316t-darwin.so:arm64+0xe5f0)
    #2 _PyObject_GenericSetAttrWithDict object.c:2049 (python.exe:arm64+0x1000dd900)
    #3 pythread_wrapper thread_pthread.h:234 (python.exe:arm64+0x10026e378)

  Previous read of size 8 at 0x000126f10588 by thread T13:
    #0 _servername_callback _ssl.c:5159 (_ssl.cpython-316t-darwin.so:arm64+0xffa0)
    #1 final_server_name <null> (libssl.3.dylib:arm64+0x5c31c)
    #2 _PyEval_EvalFrameDefault generated_cases.c.h:4142 (python.exe:arm64+0x1001c5b50)
    #3 pythread_wrapper thread_pthread.h:234 (python.exe:arm64+0x10026e378)

  Thread T29 (tid=707684, running) created by main thread at:
    #0 pthread_create <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64+0x31d84)
    #1 do_start_joinable_thread thread_pthread.h:281 (python.exe:arm64+0x10026d9f8)
    #2 do_start_new_thread _threadmodule.c:1919 (python.exe:arm64+0x10032782c)
    #3 thread_PyThread_start_joinable_thread _threadmodule.c:2042 (python.exe:arm64+0x100326894)
    #4 cfunction_call methodobject.c:564 (python.exe:arm64+0x1000d27b4)

  Thread T13 (tid=707668, running) created by main thread at:
    #0 pthread_create <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64+0x31d84)
    #1 do_start_joinable_thread thread_pthread.h:281 (python.exe:arm64+0x10026d9f8)
    #2 do_start_new_thread _threadmodule.c:1919 (python.exe:arm64+0x10032782c)
    #3 thread_PyThread_start_joinable_thread _threadmodule.c:2042 (python.exe:arm64+0x100326894)
    #4 cfunction_call methodobject.c:564 (python.exe:arm64+0x1000d27b4)

SUMMARY: ThreadSanitizer: data race _ssl.c:5304 in _ssl__SSLContext_sni_callback_set_impl
==================
Warning -- Unraisable exception
Exception ignored in ssl servername callback while calling set SNI callback <NULL>:
Traceback (most recent call last):
  File "/Users/kignatev/PycharmProjects/cpython/Lib/ssl.py", line 963, in do_handshake
    self._sslobj.do_handshake()
    ~~~~~~~~~~~~~~~~~~~~~~~~~^^
SystemError: null argument to internal routine
Fatal Python error: Segmentation fault

<Cannot show all threads while the GIL is disabled>
Stack (most recent call first):
  <invalid frame>

Current thread's C stack trace (most recent call first):
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _Py_DumpStack+0x44 [0x104db912c]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at faulthandler_fatal_error+0x330 [0x104dddf98]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at _ZN6__tsanL21CallUserSignalHandlerEPNS_11ThreadStateEbbiPN11__sanitizer23__sanitizer_siginfo_padEPv+0x104 [0x10570f910]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at _Z10sighandleriPN11__sanitizer23__sanitizer_siginfo_padEPv+0x1a8 [0x10570fb68]
  Binary file "/usr/lib/system/libsystem_platform.dylib", at _sigtramp+0x38 [0x182e257a4]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_EvalFrameDefault+0xc71c [0x104d152e4]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_Vector+0x2d8 [0x104d076ec]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at object_vacall+0x138 [0x104babb78]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at PyObject_CallFunctionObjArgs+0x38 [0x104babce0]
  Binary file "/Users/kignatev/PycharmProjects/cpython/Modules/_ssl.cpython-316t-darwin.so", at _servername_callback+0x274 [0x10f9c01c8]
  Binary file "/opt/homebrew/Cellar/openssl@3/3.6.2/lib/libssl.3.dylib", at final_server_name+0x6c [0x113db4320]
  Binary file "/opt/homebrew/Cellar/openssl@3/3.6.2/lib/libssl.3.dylib", at tls_parse_all_extensions+0xa8 [0x113db3a10]
  Binary file "/opt/homebrew/Cellar/openssl@3/3.6.2/lib/libssl.3.dylib", at tls_post_process_client_hello+0x560 [0x113dcf678]
  Binary file "/opt/homebrew/Cellar/openssl@3/3.6.2/lib/libssl.3.dylib", at state_machine+0x59c [0x113dbe824]
  Binary file "/Users/kignatev/PycharmProjects/cpython/Modules/_ssl.cpython-316t-darwin.so", at _ssl__SSLSocket_do_handshake+0x184 [0x10f9c093c]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_EvalFrameDefault+0x4f8c [0x104d0db54]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_Vector+0x2d8 [0x104d076ec]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyObject_VectorcallPrepend+0x144 [0x104bab0c8]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at context_run+0x88 [0x104d3b77c]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at PyObject_Vectorcall+0x58 [0x104ba9a40]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _Py_VectorCallInstrumentation_StackRefSteal+0x12c [0x104d07d10]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_EvalFrameDefault+0x21b4 [0x104d0ad7c]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_Vector+0x2d8 [0x104d076ec]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyObject_VectorcallPrepend+0x144 [0x104bab0c8]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at thread_run+0xe0 [0x104e6ff58]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at pythread_wrapper+0x1c [0x104db637c]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at __tsan_thread_start_func+0x8c [0x105709cf8]
  Binary file "/usr/lib/system/libsystem_pthread.dylib", at _pthread_start+0x88 [0x182e1bc58]
  Binary file "/usr/lib/system/libsystem_pthread.dylib", at thread_start+0x8 [0x182e16c1c]
ThreadSanitizer:DEADLYSIGNAL
==68672==ERROR: ThreadSanitizer: SEGV on unknown address 0x000000000000 (pc 0x000104d0ef10 bp 0x00017e422240 sp 0x00017e421fe0 T707674)
==68672==The signal is caused by a READ memory access.
==68672==Hint: address points to the zero page.
Warning -- Unraisable exception
Exception ignored in ssl servername callback while calling set SNI callback <NULL>:
Traceback (most recent call last):
  File "/Users/kignatev/PycharmProjects/cpython/Lib/ssl.py", line 963, in do_handshake
    self._sslobj.do_handshake()
    ~~~~~~~~~~~~~~~~~~~~~~~~~^^
SystemError: null argument to internal routine
    #0 _PyEval_EvalFrameDefault generated_cases.c.h:5550 (python.exe:arm64+0x1001c6f10)
    #1 _PyEval_EvalFrame pycore_ceval.h:122 (python.exe:arm64+0x1001bf6e8)
    #2 _PyEval_Vector ceval.c:2156 (python.exe:arm64+0x1001bf6e8)
    #3 _PyObject_VectorcallTstate pycore_call.h:144 (python.exe:arm64+0x100063b74)
    #4 object_vacall call.c:823 (python.exe:arm64+0x100063b74)
    #5 PyObject_CallFunctionObjArgs call.c:977 (python.exe:arm64+0x100063cdc)
    #6 _servername_callback _ssl.c:5214 (_ssl.cpython-316t-darwin.so:arm64+0x101c4)
    #7 final_server_name <null> (libssl.3.dylib:arm64+0x5c31c)
    #8 tls_parse_all_extensions <null> (libssl.3.dylib:arm64+0x5ba0c)
    #9 tls_post_process_client_hello <null> (libssl.3.dylib:arm64+0x77674)
    #10 state_machine <null> (libssl.3.dylib:arm64+0x66820)
    #11 _ssl__SSLSocket_do_handshake_impl _ssl.c:1098 (_ssl.cpython-316t-darwin.so:arm64+0x10938)
    #12 _ssl__SSLSocket_do_handshake _ssl.c.h:30 (_ssl.cpython-316t-darwin.so:arm64+0x10938)
    #13 _PyEval_EvalFrameDefault generated_cases.c.h:4142 (python.exe:arm64+0x1001c5b50)
    #14 _PyEval_EvalFrame pycore_ceval.h:122 (python.exe:arm64+0x1001bf6e8)
    #15 _PyEval_Vector ceval.c:2156 (python.exe:arm64+0x1001bf6e8)
    #16 _PyObject_VectorcallTstate pycore_call.h:144 (python.exe:arm64+0x1000630c4)
    #17 _PyObject_VectorcallPrepend call.c:855 (python.exe:arm64+0x1000630c4)
    #18 _PyObject_VectorcallTstate pycore_call.h:144 (python.exe:arm64+0x1001f3778)
    #19 context_run context.c:727 (python.exe:arm64+0x1001f3778)
    #20 _PyObject_VectorcallTstate pycore_call.h:144 (python.exe:arm64+0x100061a3c)
    #21 PyObject_Vectorcall call.c:327 (python.exe:arm64+0x100061a3c)
    #22 _Py_VectorCallInstrumentation_StackRefSteal ceval.c:775 (python.exe:arm64+0x1001bfd0c)
    #23 _PyEval_EvalFrameDefault generated_cases.c.h:1846 (python.exe:arm64+0x1001c2d78)
    #24 _PyEval_EvalFrame pycore_ceval.h:122 (python.exe:arm64+0x1001bf6e8)
    #25 _PyEval_Vector ceval.c:2156 (python.exe:arm64+0x1001bf6e8)
    #26 _PyObject_VectorcallTstate pycore_call.h:144 (python.exe:arm64+0x1000630c4)
    #27 _PyObject_VectorcallPrepend call.c:855 (python.exe:arm64+0x1000630c4)
    #28 thread_run _threadmodule.c:388 (python.exe:arm64+0x100327f54)
    #29 pythread_wrapper thread_pthread.h:234 (python.exe:arm64+0x10026e378)
    #30 __tsan_thread_start_func <null> (libclang_rt.tsan_osx_dynamic.dylib:arm64+0x31cf4)
    #31 _pthread_start <null> (libsystem_pthread.dylib:arm64e+0x6c54)
    #32 thread_start <null> (libsystem_pthread.dylib:arm64e+0x1c18)

==68672==Register values:
 x[0] = 0x000000010e21dc88   x[1] = 0x00000001171c02e8   x[2] = 0x0000000000000000   x[3] = 0x000000017e422250
 x[4] = 0x0000000000000003   x[5] = 0x0000000000000000   x[6] = 0x0000000000000000   x[7] = 0x0000000000366b00
 x[8] = 0x0000000000000030   x[9] = 0x00000001171c0338  x[10] = 0x0000000000000001  x[11] = 0x0000000000000003
x[12] = 0x000000010505bda1  x[13] = 0x0000000000000003  x[14] = 0x0000000000000075  x[15] = 0x00000001eec259a0
x[16] = 0x0000000000000018  x[17] = 0x000000010e21dc70  x[18] = 0x0000000000000000  x[19] = 0x00000001171c0328
x[20] = 0x00000001171c0358  x[21] = 0x0000000104fd7da8  x[22] = 0x000000030e1001c0  x[23] = 0x000000030e1001c0
x[24] = 0x0000000000000000  x[25] = 0x0000000000000001  x[26] = 0x000000000000001d  x[27] = 0x00000001171c02e8
x[28] = 0x00000001240b8000     fp = 0x000000017e422240     lr = 0x0000000104d152e4     sp = 0x000000017e421fe0
ThreadSanitizer can not provide additional info.
SUMMARY: ThreadSanitizer: SEGV generated_cases.c.h:5550 in _PyEval_EvalFrameDefault
==68672==ABORTING
Fatal Python error: Aborted

<Cannot show all threads while the GIL is disabled>
Stack (most recent call first):
  <invalid frame>

Current thread's C stack trace (most recent call first):
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _Py_DumpStack+0x44 [0x104db912c]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at faulthandler_fatal_error+0x330 [0x104dddf98]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at _ZN6__tsanL21CallUserSignalHandlerEPNS_11ThreadStateEbbiPN11__sanitizer23__sanitizer_siginfo_padEPv+0x104 [0x10570f910]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at _Z10sighandleriPN11__sanitizer23__sanitizer_siginfo_padEPv+0x1a8 [0x10570fb68]
  Binary file "/usr/lib/system/libsystem_platform.dylib", at _sigtramp+0x38 [0x182e257a4]
  Binary file "/usr/lib/system/libsystem_pthread.dylib", at pthread_kill+0x128 [0x182e1b8d8]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at wrap_pthread_kill+0x134 [0x105710278]
  Binary file "/usr/lib/system/libsystem_c.dylib", at abort+0x94 [0x182d22790]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at _ZN11__sanitizer6AtexitEPFvvE+0x0 [0x1056f11b4]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at _ZN11__sanitizer3DieEv+0x68 [0x1056f06e4]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at _ZN11__sanitizer13SignalContextC1EPvS1_+0x0 [0x1056fd974]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at _ZN6__tsanL21CallUserSignalHandlerEPNS_11ThreadStateEbbiPN11__sanitizer23__sanitizer_siginfo_padEPv+0x104 [0x10570f910]
  Binary file "/opt/homebrew/Cellar/llvm/22.1.5/lib/clang/22/lib/darwin/libclang_rt.tsan_osx_dynamic.dylib", at _Z10sighandleriPN11__sanitizer23__sanitizer_siginfo_padEPv+0x1a8 [0x10570fb68]
  Binary file "/usr/lib/system/libsystem_platform.dylib", at _sigtramp+0x38 [0x182e257a4]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_EvalFrameDefault+0xc71c [0x104d152e4]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_Vector+0x2d8 [0x104d076ec]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at object_vacall+0x138 [0x104babb78]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at PyObject_CallFunctionObjArgs+0x38 [0x104babce0]
  Binary file "/Users/kignatev/PycharmProjects/cpython/Modules/_ssl.cpython-316t-darwin.so", at _servername_callback+0x274 [0x10f9c01c8]
  Binary file "/opt/homebrew/Cellar/openssl@3/3.6.2/lib/libssl.3.dylib", at final_server_name+0x6c [0x113db4320]
  Binary file "/opt/homebrew/Cellar/openssl@3/3.6.2/lib/libssl.3.dylib", at tls_parse_all_extensions+0xa8 [0x113db3a10]
  Binary file "/opt/homebrew/Cellar/openssl@3/3.6.2/lib/libssl.3.dylib", at tls_post_process_client_hello+0x560 [0x113dcf678]
  Binary file "/opt/homebrew/Cellar/openssl@3/3.6.2/lib/libssl.3.dylib", at state_machine+0x59c [0x113dbe824]
  Binary file "/Users/kignatev/PycharmProjects/cpython/Modules/_ssl.cpython-316t-darwin.so", at _ssl__SSLSocket_do_handshake+0x184 [0x10f9c093c]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_EvalFrameDefault+0x4f8c [0x104d0db54]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_Vector+0x2d8 [0x104d076ec]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyObject_VectorcallPrepend+0x144 [0x104bab0c8]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at context_run+0x88 [0x104d3b77c]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at PyObject_Vectorcall+0x58 [0x104ba9a40]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _Py_VectorCallInstrumentation_StackRefSteal+0x12c [0x104d07d10]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_EvalFrameDefault+0x21b4 [0x104d0ad7c]
  Binary file "/Users/kignatev/PycharmProjects/cpython/python.exe", at _PyEval_Vector+0x2d8 [0x104d076ec]
  <truncated rest of calls>
zsh: abort      ./python.exe -m test test_ssl -m test_sni_callback_race

After

0:00:00 load avg: 4.18 [1/1] test_ssl passed

Using Repro:

% ./python.exe cpython-ft/repros/49.py
finding: 49 SSLContext.sni_callback replacement race
expected signal: native crash/fatal error/sanitizer use-after-free during concurrent SNI handshakes
parameters: seconds=10; Python=3.16.0a0; GIL_enabled=False; workers=28
------------------------------------------------------------------------
Completed without interpreter crash: 53271 handshakes, 0 Python-level failures, 245825 toggles.

More info

@bedevere-app bedevere-app Bot added the tests Tests in the Lib/test dir label May 18, 2026
@python-cla-bot

python-cla-bot Bot commented May 18, 2026 •
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All commit authors signed the Contributor License Agreement.

CLA signed

@bedevere-app

bedevere-app Bot commented May 18, 2026

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

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bedevere-app Bot commented May 18, 2026

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

@kiri11 kiri11 changed the title Add test_sni_callback_race May 18, 2026
@bedevere-app bedevere-app Bot mentioned this pull request May 18, 2026
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Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

@kiri11 kiri11 marked this pull request as ready for review May 19, 2026 00:17
@kiri11 kiri11 requested review from gpshead and picnixz as code owners May 19, 2026 00:17
@cmaloney cmaloney added the label May 19, 2026
@github-project-automation github-project-automation Bot moved this to Todo in Sprint May 19, 2026
@kiri11 kiri11 requested a review from encukou May 19, 2026 01:41
@encukou encukou added the needs backport to 3.13 bugs and security fixes label May 19, 2026
@encukou encukou added needs backport to 3.14 bugs and security fixes needs backport to 3.15 pre-release feature fixes, bugs and security fixes labels May 19, 2026
Hide details View details @encukou encukou merged commit 8b31d08 into python:main May 19, 2026
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miss-islington-app Bot commented May 19, 2026

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Thanks @kiri11 for the PR, and @encukou for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14, 3.15.
🐍🍒⛏🤖

@github-project-automation github-project-automation Bot moved this from Todo to Done in Sprint May 19, 2026
@miss-islington-app

miss-islington-app Bot commented May 19, 2026

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Sorry, @kiri11 and @encukou, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 8b31d08e62b9714cf8dd1d8b19afa5ecbad2414a 3.13

@bedevere-app

bedevere-app Bot commented May 19, 2026

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GH-150099 is a backport of this pull request to the 3.15 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.15 pre-release feature fixes, bugs and security fixes label May 19, 2026
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bedevere-app Bot commented May 19, 2026

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GH-150100 is a backport of this pull request to the 3.14 branch.

@bedevere-app bedevere-app Bot removed the needs backport to 3.14 bugs and security fixes label May 19, 2026
@encukou encukou removed the needs backport to 3.13 bugs and security fixes label May 19, 2026
encukou pushed a commit that referenced this pull request May 19, 2026
@miss-islington @kiri11
[3.14] gh-149816: Fix SNI callback callable race (GH-150018) (GH-150100) …
2744371 
(cherry picked from commit 8b31d08)

Co-authored-by: Kirill Ignatev <kiri11@users.noreply.github.com>
@colesbury colesbury mentioned this pull request May 21, 2026
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serhiy-storchaka pushed a commit that referenced this pull request Jun 8, 2026
@miss-islington @kiri11 @encukou
[3.15] gh-149816: Fix SNI callback callable race (GH-150018) (GH-150099) …
9997975 
(cherry picked from commit 8b31d08)

Co-authored-by: Kirill Ignatev <kiri11@users.noreply.github.com>
Co-authored-by: Petr Viktorin <encukou@gmail.com>
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