Description
ssl.SSLContext.wrap_bio() didn't require the server_hostname argument
to not be None if ssl.SSLContext.check_hostname was set. Due to a
missing parameter check in SSLObject, if the server_hostname argument
isn't supplied then hostname verification would be silently skipped.
This defect could lead to programs where certificate hostname verification
*appeared* to be succeeding with SSLContext.check_hostname = True and no
ValueError being raised due to misconfiguration.
If the program passes a server_hostname value that isn't an empty string
or None to any of these APIs then certificate hostname verification
proceeds as expected and the program is not affected by this vulnerability.
Mitigating this vulnerability doesn't require updating Python or applying
the patch. To mitigate, pass a valid non-None and non-empty
server_hostname value to SSLContext.wrap_bio(),
asyncio.create_connection(), or asyncio.loop.start_tls() and
certificate hostname verification will proceed as expected. Upgrading to
the latest version of Python or applying the patch only changes the
behavior from silently skipping hostname verification to raising a
ValueError, similar to SSLContext.wrap_socket(), when server_hostname
isn't supplied.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Python Software Foundation | CPython | < 3.10.22, 3.11.0 – < 3.11.17, 3.12.0 – < 3.12.15, 3.13.0 – < 3.13.16, 3.14.0 – < 3.14.8, 3.15.0a1 – < 3.15.0rc3 | 3.10.22 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | pypy3 | 8.0.1+dfsg-1 | — |
| Debian 14 | python3.14 | 3.14.8-1 | — |
| Debian 14 | python3.15 | 3.15.0~rc3-1 | — |
| Debian 13 | pypy3 +1 | No fix yet | — |
| Debian 12 | pypy3 | No fix yet | — |
| Debian 12 | python3.11 | 3.11.2-6+deb12u9 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | python3.14 | No fix yet | — |
| Ubuntu 26.04 LTS | python3.14 | No fix yet | — |
| Ubuntu 24.04 LTS | python3.12 | No fix yet | — |
| Ubuntu 22.04 LTS | python3.10 | No fix yet | — |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 22.04 LTS | python2.7 +1 | No fix yet | — |
| Ubuntu Pro 20.04 LTS | python2.7 +2 | No fix yet | — |
| Ubuntu Pro 18.04 LTS | python2.7 +3 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | python2.7 +1 | No fix yet | — |
| Ubuntu Pro 14.04 LTS | python2.7 +2 | No fix yet | — |
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 10 | python3 +8 | 3.12.15-1.el10_2 | RHSA-2026:77020 |
| RHEL 10 | python3.14 +13 | 3.14.8-1.el10_2 | RHSA-2026:77018 |
| RHEL 9 | python3 +8 | 3.9.25-7.el9_8.6 | RHSA-2026:98511, RHSA-2026:89742 |
| RHEL 9 | python3.12 +6 | 3.12.15-1.el9_8 | RHSA-2026:77017 |
| RHEL 9 | python3.14 +13 | 3.14.8-1.el9_8 | RHSA-2026:77021 |
| RHEL 8 | python3 +7 | 3.6.8-79.el8_10 | RHSA-2026:85239 |
| RHEL 8 | python3.12 +7 | 3.12.15-2.el8_10 | RHSA-2026:77028 |
Show 5 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 8.6 EUS Long Life | python3 +7 | 3.6.8-47.el8_6.16 | RHSA-2026:94443 |
| RHEL 8.6 AUS | python3 +7 | 3.6.8-47.el8_6.16 | RHSA-2026:94443 |
| RHEL 8.4 EUS Long Life | python3 +7 | 3.6.8-39.el8_4.13 | RHSA-2026:95082 |
| RHEL 8.4 AUS | python3 +7 | 3.6.8-39.el8_4.13 | RHSA-2026:95082 |
| Red Hat Hardened Images 1 | python3 +15 | 3.14.7-1.3.hum1 | RHSA-2026:74587 |
| Red Hat Hardened Images 1 | python3.10 +6 | 3.10.21-1.5.hum1 | RHSA-2026:74594 |
| Red Hat Hardened Images 1 | python3.11 +6 | 3.11.16-1.5.hum1 | RHSA-2026:74599 |
| Red Hat Hardened Images 1 | python3.12 +6 | 3.12.14-1.4.hum1 | RHSA-2026:74606 |
| Red Hat Hardened Images 1 | python3.13 +8 | 3.13.15-1.4.hum1 | RHSA-2026:74605 |
AlmaLinux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| AlmaLinux 10 | python3 +7 | 3.12.15-1.el10_2 | ALSA-2026:77020 |
| AlmaLinux 10 | python3.14 +13 | 3.14.8-1.el10_2 | ALSA-2026:77018 |
| AlmaLinux 9 | python3 +7 | 3.9.25-7.el9_8.6 | ALSA-2026:89742 |
| AlmaLinux 9 | python3.12 +6 | 3.12.15-1.el9_8 | ALSA-2026:77017 |
| AlmaLinux 9 | python3.14 +13 | 3.14.8-1.el9_8 | ALSA-2026:77021 |
| AlmaLinux 8 | python3-idle +6 | 3.6.8-79.el8_10.alma.1 | ALSA-2026:85239 |
| AlmaLinux 8 | python3.12 +7 | 3.12.15-2.el8_10 | ALSA-2026:77028 |
Rocky Linux
Errata ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Rocky Linux 10 | python3.12 | 3.12.15-1.el10_2 | RLSA-2026:77020 |
| Rocky Linux 10 | python3.14 | 3.14.8-1.el10_2 | RLSA-2026:77018 |
| Rocky Linux 9 | python3.12 | 3.12.15-1.el9_8 | RLSA-2026:77017 |
| Rocky Linux 9 | python3.14 | 3.14.8-1.el9_8 | RLSA-2026:77021 |
| Rocky Linux 9 | python3.9 | 3.9.25-7.el9_8.6 | RLSA-2026:89742 |
| Rocky Linux 8 | python3 | 3.6.8-79.el8_10.rocky.0 | RLSA-2026:85239 |
| Rocky Linux 8 | python3.12 | 3.12.15-2.el8_10 | RLSA-2026:77028 |
SUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES 15 SP7 | python311-core | 3.11.17-150600.3.74.1 | SUSE-SU-2026:4946-1 |
| SLES 15 SP6 | python311 +1 | 3.11.17-150600.3.74.1 | SUSE-SU-2026:4946-1 |
| SLES 15 SP6 | python312 +1 | 3.12.15-150600.3.71.1 | SUSE-SU-2026:4659-1 |
| SLES 15 SP5 | python311 +2 | 3.11.17-150400.9.105.1 | SUSE-SU-2026:4809-1 |
| SLES 15 SP4 | python310 +1 | 3.10.22-150400.4.129.1 | SUSE-SU-2026:4630-1 |
| SLES 15 SP4 | python311 +2 | 3.11.17-150400.9.105.1 | SUSE-SU-2026:4809-1 |
| SLES 3 | python311 +1 | 3.11.17-150600.3.74.1 | SUSE-SU-2026:4946-1 |
| SLES 3 | python313 +1 | 3.13.16-150700.4.61.1 | SUSE-SU-2026:4941-1 |
Show 7 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| SLES for SAP 15 SP6 | python311 +1 | 3.11.17-150600.3.74.1 | SUSE-SU-2026:4946-1 |
| SLES for SAP 15 SP6 | python312 +1 | 3.12.15-150600.3.71.1 | SUSE-SU-2026:4659-1 |
| SLES for SAP 15 SP5 | python311 +2 | 3.11.17-150400.9.105.1 | SUSE-SU-2026:4809-1 |
| SLES for SAP 15 SP4 | python310 +1 | 3.10.22-150400.4.129.1 | SUSE-SU-2026:4630-1 |
| SLES for SAP 15 SP4 | python311 +2 | 3.11.17-150400.9.105.1 | SUSE-SU-2026:4809-1 |
| SLE Micro 6.1 | python311 +1 | 3.11.17-slfo.1.1_1.1 | SUSE-SU-2026:24280-1 |
| SLE Micro 6.0 | python311 +1 | 3.11.17-159998.1.1 | SUSE-SU-2026:24325-1 |
| SLE HPC 15 SP5 | python311 +2 | 3.11.17-150400.9.105.1 | SUSE-SU-2026:4809-1 |
| SLE HPC 15 SP4 | python310 +1 | 3.10.22-150400.4.129.1 | SUSE-SU-2026:4630-1 |
| SLE HPC 15 SP4 | python311 +2 | 3.11.17-150400.9.105.1 | SUSE-SU-2026:4809-1 |
openSUSE
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| openSUSE Tumbleweed | python310 | 3.10.22-1.1 | openSUSE-SU-2026:12087-1 |
| openSUSE Tumbleweed | python311 | 3.11.17-1.1 | openSUSE-SU-2026:12121-1 |
| openSUSE Tumbleweed | python312 | 3.12.15-1.1 | openSUSE-SU-2026:12122-1 |
| openSUSE Tumbleweed | python313 | 3.13.16-1.1 | openSUSE-SU-2026:12123-1 |
| openSUSE Tumbleweed | python314 | 3.14.8-1.1 | openSUSE-SU-2026:12124-1 |
| openSUSE Tumbleweed | python315 | 3.15.0~rc3-1.1 | openSUSE-SU-2026:12069-1 |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | python3 | 3.14.8-r0 | — |
| Alpine v3.23 | python3 | 3.12.15-r0 | — |
| Alpine v3.22 | python3 | 3.12.15-r0 | — |
| Alpine v3.21 | python3 | 3.12.15-r0 | — |
Amazon Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Amazon Linux 2023 | python3 +7 | 3.9.25-1.amzn2023.0.11 | ALAS2023-2026-3278 |
| Amazon Linux 2023 | python3.11 +6 | 3.11.17-1.amzn2023.0.1 | ALAS2023-2026-3231 |
| Amazon Linux 2023 | python3.12 +6 | 3.12.15-2.amzn2023.0.1 | ALAS2023-2026-3230 |
| Amazon Linux 2023 | python3.13 +8 | 3.13.16-1.amzn2023.0.1 | ALAS2023-2026-3229 |
| Amazon Linux 2023 | python3.14 +13 | 3.14.8-1.amzn2023.0.1 | ALAS2023-2026-3232 |
| Amazon Linux 2 | python3 +6 | 3.7.16-1.amzn2.0.30 | ALAS2-2026-4025 |
Azure Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Azure Linux 3 | python3 +1 | No fix yet | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 10 | python3 +7 | 3.12.15-1.0.1.el10_2 | ELSA-2026-77020 |
| Oracle Linux 10 | python3.14 +13 | 3.14.8-1.el10_2 | ELSA-2026-77018 |
| Oracle Linux 9 | python3 +7 | 3.9.25-7.0.1.el9_8.6 | ELSA-2026-89742 |
| Oracle Linux 9 | python3.12 +6 | 3.12.15-1.0.1.el9_8 | ELSA-2026-77017 |
| Oracle Linux 9 | python3.14 +13 | 3.14.8-1.el9_8 | ELSA-2026-77021 |
| Oracle Linux 8 | python3-idle +6 | 3.6.8-79.0.1.el8_10 | ELSA-2026-85239 |
| Oracle Linux 8 | python3.12 +7 | 3.12.15-2.el8_10 | ELSA-2026-77028 |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.
GitHub 3 repositories
-
monkeyyey/acw3-tls-lab ★ 0 · Nov 8, 2026
Local CVE-2026-19553 TLS lab with a guarded Ubuntu 24.04 setup and seven demonstration tests.
-
Tharsh2003/INF2005-ACW3-PythonSSL ★ 0 · Nov 4, 2026
INF2005 ACW3 - CVE-2026-19553 Exploitation
-
abraxas/cve-2026-19553-wrap-bio ★ 0 · Oct 2, 2026
CPython - High - wrap_bio hostname skip
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 50
- RHSA-2026:98511 Red Hat Security Advisory: python3.9 security update Red Hat Security Advisories (RHSA) · Nov 13, 2026
- RHSA-2026:95082 Red Hat Security Advisory: python3 security update Red Hat Security Advisories (RHSA) · Nov 13, 2026
- RHSA-2026:94443 Red Hat Security Advisory: python3 security update Red Hat Security Advisories (RHSA) · Nov 13, 2026
- RHSA-2026:89742 Red Hat Security Advisory: python3.9 security update Red Hat Security Advisories (RHSA) · Nov 13, 2026
- WID-SEC-2026-3716 CPython: Mehrere Schwachstellen BSI CERT-Bund (WID) · Nov 12, 2026
- SSA-457936 SSA-457936: Vulnerabilities in the additional GNU/Linux subsystem of the SIMATIC S7-1500 CPU 1518(F)-4 PN/DP MFP V3.1.7 Siemens ProductCERT · Nov 10, 2026
- SUSE-SU-2026:4946-1 Security update for python311 SUSE / openSUSE Security Updates · Oct 31, 2026
- SUSE-SU-2026:4941-1 Security update for python313 SUSE / openSUSE Security Updates · Oct 31, 2026
- ALSA-2026:77017 Important: python3.12 security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:77021 Important: python3.14 security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:89742 Important: python3.9 security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:77018 Important: python3.14 security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:77020 Important: python3.12 security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:77028 Important: python3.12 security update AlmaLinux Security Advisories · Oct 29, 2026
- ALSA-2026:85239 Important: python3 security update AlmaLinux Security Advisories · Oct 29, 2026
- SUSE-SU-2026:24325-1 Security update for python311 SUSE / openSUSE Security Updates · Oct 27, 2026
- SUSE-SU-2026:24280-1 Security update for python311 SUSE / openSUSE Security Updates · Oct 27, 2026
- RLSA-2026:89742 Important: python3.9 security update Rocky Linux Security Advisories · Oct 27, 2026
- ALAS2023-2026-3229 Important: python3.13 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 26, 2026
- ALAS2023-2026-3230 Important: python3.12 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 26, 2026
- ALAS2023-2026-3231 Important: python3.11 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 26, 2026
- ALAS2023-2026-3232 Important: python3.14 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 26, 2026
- ALAS2023-2026-3278 Important: python3.9 security update (Amazon Linux 2023) Amazon Linux Security Center (ALAS) · Oct 26, 2026
- ALAS2-2026-4025 Important: python3 security update (Amazon Linux 2) Amazon Linux Security Center (ALAS) · Oct 26, 2026
- ELSA-2026-89742 Important: python3.9 security update (Oracle Linux 9) Oracle Linux Security Advisories (ELSA) · Oct 26, 2026
- SUSE-SU-2026:4809-1 Security update for python311 SUSE / openSUSE Security Updates · Oct 21, 2026
- RLSA-2026:85239 Important: python3 security update Rocky Linux Security Advisories · Oct 21, 2026
- RHSA-2026:85239 Red Hat Security Advisory: python3 security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:77021 Red Hat Security Advisory: python3.14 security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:77028 Red Hat Security Advisory: python3.12 security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:77020 Red Hat Security Advisory: python3.12 security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:77017 Red Hat Security Advisory: python3.12 security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:77018 Red Hat Security Advisory: python3.14 security update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:74605 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:74606 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:74599 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:74587 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- RHSA-2026:74594 Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update Red Hat Security Advisories (RHSA) · Oct 20, 2026
- ELSA-2026-85239 Important: python3 security update (Oracle Linux 8) Oracle Linux Security Advisories (ELSA) · Oct 20, 2026
- SUSE-SU-2026:4659-1 Security update for python312 SUSE / openSUSE Security Updates · Oct 14, 2026
- openSUSE-SU-2026:12124-1 python314-3.14.8-1.1 on GA media SUSE / openSUSE Security Updates · Oct 14, 2026
- openSUSE-SU-2026:12121-1 python311-3.11.17-1.1 on GA media SUSE / openSUSE Security Updates · Oct 14, 2026
- openSUSE-SU-2026:12122-1 python312-3.12.15-1.1 on GA media SUSE / openSUSE Security Updates · Oct 14, 2026
- openSUSE-SU-2026:12123-1 python313-3.13.16-1.1 on GA media SUSE / openSUSE Security Updates · Oct 14, 2026
- SUSE-SU-2026:4630-1 Security update for python310 SUSE / openSUSE Security Updates · Oct 13, 2026
- openSUSE-SU-2026:12087-1 python310-3.10.22-1.1 on GA media SUSE / openSUSE Security Updates · Oct 9, 2026
- RLSA-2026:77017 Important: python3.12 security update Rocky Linux Security Advisories · Oct 9, 2026
- RLSA-2026:77018 Important: python3.14 security update Rocky Linux Security Advisories · Oct 9, 2026
- RLSA-2026:77020 Important: python3.12 security update Rocky Linux Security Advisories · Oct 9, 2026
- RLSA-2026:77021 Important: python3.14 security update Rocky Linux Security Advisories · Oct 9, 2026
References
- https://github.com/python/cpython/pull/158503 patch
- https://github.com/python/cpython/issues/156793 issue-tracking
- https://mail.python.org/archives/list/security-announce@python.org/thread/QNZRG3YOAMTHDCMVCICXGY6YEFPY2VDL/ vendor-advisory
- https://github.com/python/cpython/commit/1697ea386c707142555d98a1263176bbbc014a96 patch
- https://github.com/python/cpython/commit/641390146a16a38e6701923f4ee4f1940ae77082 patch
- https://github.com/python/cpython/commit/966bf426d0b6c31c1b0a255ff14a17143a466ced patch
- https://github.com/python/cpython/commit/f4e43ba525187282f2011da0e6ffc0d2b08d8062 patch
- https://github.com/python/cpython/commit/869069d52ce0efab2f8c38197e92cdaaa312f1ed patch
- https://github.com/python/cpython/commit/5867d4e4ae6d1062352baf6b497a4026e8578ccf patch
- https://github.com/python/cpython/commit/bdebbf9b366ec91e9cd9daa0b3510c9e84b60b80 patch