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Fencer Vulns
high 7.6

CVE-2026-19553 json

SSLContext.wrap_bio() missing validation of server_hostname parameter

published 2026-09-30 40 d ago modified 2026-10-16 23 d ago also BIT-libpython-2026-19553 , BIT-python-2026-19553 , BIT-python-min-2026-19553 , EUVD-2026-90078

cvss
7.6
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami libpython 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.8
  • bitnami python 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.8
  • bitnami python-min 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.8
  • Python Software Foundation CPython 3.10.22, 3.11.17, 3.12.15, 3.13.16, 3.14.8, 3.15.0rc3
  • pypy3 Debian 14 8.0.1+dfsg-1
  • python3.11 Debian 12 3.11.2-6+deb12u9
  • python3.14 Debian 14 3.14.8-1
  • python3.15 Debian 14 3.15.0~rc3-1

debian advisories DEBIAN-CVE-2026-19553

  • python3 RHEL 8 3.6.8-79.el8_10
  • python3-idle RHEL 8 3.6.8-79.el8_10
  • python3-libs RHEL 8 3.6.8-79.el8_10
  • python3-test RHEL 8 3.6.8-79.el8_10
  • platform-python RHEL 8 3.6.8-79.el8_10
  • python3-tkinter RHEL 8 3.6.8-79.el8_10
  • python3.14 RHEL 9 3.14.8-1.el9_8
  • python3.14-idle RHEL 9 3.14.8-1.el9_8

red hat advisories RHSA-2026:85239RHSA-2026:77021RHSA-2026:77020RHSA-2026:77018RHSA-2026:77017RHSA-2026:77028

  • python311 SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Python 3 15 SP7 3.11.17-150600.3.74.1
  • python311-core SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Python 3 15 SP7 +1 more 3.11.17-150600.3.74.1
  • python313 SLE Module for Python 3 15 SP7 3.13.16-150700.4.61.1
  • python313-core SLE Module for Python 3 15 SP7 3.13.16-150700.4.61.1
  • python311 SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +6 more 3.11.17-150400.9.105.1
  • python311-core SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +6 more 3.11.17-150400.9.105.1
  • python311-documentation SLES for SAP 15 SP5, SLES for SAP 15 SP4, SLES 15 SP5-LTSS +5 more 3.11.17-150400.9.105.1
  • python311 Linux Micro 6.1 3.11.17-slfo.1.1_1.1

suse advisories SUSE-SU-2026:4946-1SUSE-SU-2026:4941-1SUSE-SU-2026:4809-1SUSE-SU-2026:24280-1SUSE-SU-2026:24325-1SUSE-SU-2026:4659-1

  • python311 openSUSE Tumbleweed 3.11.17-1.1
  • python312 openSUSE Tumbleweed 3.12.15-1.1
  • python313 openSUSE Tumbleweed 3.13.16-1.1
  • python314 openSUSE Tumbleweed 3.14.8-1.1
  • python310 openSUSE Tumbleweed 3.10.22-1.1
  • python315 openSUSE Tumbleweed 3.15.0~rc3-1.1

opensuse advisories openSUSE-SU-2026:12121-1openSUSE-SU-2026:12122-1openSUSE-SU-2026:12123-1openSUSE-SU-2026:12124-1openSUSE-SU-2026:12087-1openSUSE-SU-2026:12069-1

  • python3 AlmaLinux 9 3.9.25-7.el9_8.6
  • python3-idle AlmaLinux 9 3.9.25-7.el9_8.6
  • python3-libs AlmaLinux 9 3.9.25-7.el9_8.6
  • python3-test AlmaLinux 9 3.9.25-7.el9_8.6
  • python3-tkinter AlmaLinux 9 3.9.25-7.el9_8.6
  • python-unversioned-command AlmaLinux 9 3.9.25-7.el9_8.6
  • python3-idle AlmaLinux 8 3.6.8-79.el8_10.alma.1
  • python3-libs AlmaLinux 8 3.6.8-79.el8_10.alma.1

almalinux advisories ALSA-2026:89742ALSA-2026:85239ALSA-2026:77017ALSA-2026:77018ALSA-2026:77020ALSA-2026:77021

  • python3.9 Rocky Linux 9 3.9.25-7.el9_8.6
  • python3 Rocky Linux 8 3.6.8-79.el8_10.rocky.0
  • python3.14 Rocky Linux 10 3.14.8-1.el10_2
  • python3.12 Rocky Linux 10 3.12.15-1.el10_2
  • python3.12 Rocky Linux 9 3.12.15-1.el9_8
  • python3.14 Rocky Linux 9 3.14.8-1.el9_8
  • python3.12 Rocky Linux 8 3.12.15-2.el8_10

rocky linux advisories RLSA-2026:89742RLSA-2026:85239RLSA-2026:77018RLSA-2026:77020RLSA-2026:77017RLSA-2026:77021

  • python3 Alpine 3.23, Alpine 3.22, Alpine 3.21 3.12.15-r0
  • python3 Alpine 3.24 3.14.8-r0

alpine advisories ALPINE-CVE-2026-19553

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-19553 updated cvss 7.4

python: python: Certificate verification bypass via missing server_hostname validation in SSLContext.wrap_bio()

  • Red Hat Enterprise Linux 7 python3, python3-idle, python3-libs, python3-test, python3-tkinter
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 8 python3.11, python3.11-idle, python3.11-libs, python3.11-test, python3.11-tkinter, python3.11-rpm-macros Red Hat Enterprise Linux 9 python3.11, python3.11-idle, python3.11-libs, python3.11-test, python3.11-tkinter
    affected: workaround, no fix planned “Out of support scope”
  • Red Hat Enterprise Linux AI (RHEL AI) 3 rhelai3/bootc-cuda-rhel9, rhelai3/bootc-rocm-rhel9, rhelai3/bootc-gaudi-rhel9, rhelai3/bootc-aws-cuda-rhel9, rhelai3/bootc-gcp-cuda-rhel9, rhelai3/bootc-azure-cuda-rhel9, +1 more
    affected: workaround, no fix available, no fix planned “Will not fix”
  • Red Hat OpenShift Virtualization 4 container-native-virtualization/ocp-virt-validation-checkup-rhel9, openshift-virtualization/konflux-builds/v4-22/ocp-virt-validation-checkup-rhel9
    affected: workaround, no fix available
  • Red Hat OpenShift AI (RHOAI) rhoai/odh-dashboard-rhel9
    under investigation
  • Red Hat Ansible Automation Platform 2.2 ansible-automation-platform/bootc-automation-portal-rhel9 1792641102
    fixed: vendor fix RHSA-2026:88200
  • Red Hat Cost Management On-Premise 1 costmanagement/costmanagement-ui-rhel10 1792605272
    fixed: vendor fix RHSA-2026:87400
  • Red Hat Discovery 2 discovery/discovery-ui-rhel9 1793733716, discovery/discovery-server-rhel9 1793734080
    fixed: vendor fix RHSA-2026:94802
show 20 more
  • Red Hat Enterprise Linux AppStream (v. 8) python3.12 3.12.15-2.el8_10, python3-idle 3.6.8-79.el8_10, python3-test 3.6.8-79.el8_10, platform-python 3.6.8-79.el8_10, python3-tkinter 3.6.8-79.el8_10, python3.12-libs 3.12.15-2.el8_10, +2 more
    fixed: vendor fix RHSA-2026:85239
  • Red Hat Enterprise Linux AppStream (v. 9) python3.14 3.14.8-1.el9_8, python3.12 3.12.15-1.el9_8, python3.14-libs 3.14.8-1.el9_8, python3.12-libs 3.12.15-1.el9_8, python3-tkinter 3.9.25-7.el9_8.6, python3.14-tkinter 3.14.8-1.el9_8, +2 more
    fixed: vendor fix RHSA-2026:89742
  • Red Hat Enterprise Linux AppStream (v. 10) python3.14 3.14.8-1.el10_2, python3.14-libs 3.14.8-1.el10_2, python3-tkinter 3.12.15-1.el10_2, python3.14-tkinter 3.14.8-1.el10_2, python-unversioned-command 3.12.15-1.el10_2
    fixed: vendor fix RHSA-2026:77020
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) python3-idle 3.6.8-39.el8_4.13, python3-test 3.6.8-39.el8_4.13, platform-python 3.6.8-39.el8_4.13, python3-tkinter 3.6.8-39.el8_4.13
    fixed: vendor fix RHSA-2026:95082
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) python3-idle 3.6.8-47.el8_6.16, python3-test 3.6.8-47.el8_6.16, platform-python 3.6.8-47.el8_6.16, python3-tkinter 3.6.8-47.el8_6.16
    fixed: vendor fix RHSA-2026:94443
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) python3-idle 3.6.8-39.el8_4.13, python3-test 3.6.8-39.el8_4.13, platform-python 3.6.8-39.el8_4.13, python3-tkinter 3.6.8-39.el8_4.13
    fixed: vendor fix RHSA-2026:95082
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) python3-idle 3.6.8-47.el8_6.16, python3-test 3.6.8-47.el8_6.16, platform-python 3.6.8-47.el8_6.16, python3-tkinter 3.6.8-47.el8_6.16
    fixed: vendor fix RHSA-2026:94443
  • Red Hat Enterprise Linux BaseOS (v. 8) python3 3.6.8-79.el8_10, python3-libs 3.6.8-79.el8_10, python3-test 3.6.8-79.el8_10, platform-python 3.6.8-79.el8_10
    fixed: vendor fix RHSA-2026:85239
  • Red Hat Enterprise Linux BaseOS (v. 9) python3 3.9.25-7.el9_8.6, python3.9 3.9.25-7.el9_8.6, python3-libs 3.9.25-7.el9_8.6
    fixed: vendor fix RHSA-2026:89742
  • Red Hat Enterprise Linux BaseOS (v. 10) python3 3.12.15-1.el10_2, python3.12 3.12.15-1.el10_2, python3-libs 3.12.15-1.el10_2
    fixed: vendor fix RHSA-2026:77020
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4) python3 3.6.8-39.el8_4.13, python3-libs 3.6.8-39.el8_4.13, python3-test 3.6.8-39.el8_4.13, platform-python 3.6.8-39.el8_4.13
    fixed: vendor fix RHSA-2026:95082
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) python3 3.6.8-47.el8_6.16, python3-libs 3.6.8-47.el8_6.16, python3-test 3.6.8-47.el8_6.16, platform-python 3.6.8-47.el8_6.16
    fixed: vendor fix RHSA-2026:94443
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) python3 3.6.8-39.el8_4.13, python3-libs 3.6.8-39.el8_4.13, python3-test 3.6.8-39.el8_4.13, platform-python 3.6.8-39.el8_4.13
    fixed: vendor fix RHSA-2026:95082
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) python3 3.6.8-47.el8_6.16, python3-libs 3.6.8-47.el8_6.16, python3-test 3.6.8-47.el8_6.16, platform-python 3.6.8-47.el8_6.16
    fixed: vendor fix RHSA-2026:94443
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) python3 3.9.25-7.el9_8.6, python3.14 3.14.8-1.el9_8, python3.12 3.12.15-1.el9_8, python3-idle 3.9.25-7.el9_8.6, python3-test 3.9.25-7.el9_8.6, python3.14-idle 3.14.8-1.el9_8, +11 more
    fixed: vendor fix RHSA-2026:89742
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) python3-idle 3.12.15-1.el10_2, python3-test 3.12.15-1.el10_2, python3.14-idle 3.14.8-1.el10_2, python3.14-test 3.14.8-1.el10_2, python3.14-freethreading 3.14.8-1.el10_2, python3.14-freethreading-idle 3.14.8-1.el10_2, +3 more
    fixed: vendor fix RHSA-2026:77020
  • Red Hat Enterprise Linux CRB (v. 8) python3.12 3.12.15-2.el8_10, python3.12-idle 3.12.15-2.el8_10, python3.12-test 3.12.15-2.el8_10, python3.12-tkinter 3.12.15-2.el8_10
    fixed: vendor fix RHSA-2026:77028
  • Red Hat Hardened Images python3 3.14.7-1.3.hum1, python3.14 3.14.7-1.3.hum1, python3.10 3.10.21-1.5.hum1, python3.11 3.11.16-1.5.hum1, python3.12 3.12.14-1.4.hum1, python3.13 3.13.15-1.4.hum1, +27 more
    fixed: vendor fix RHSA-2026:74587
  • Red Hat Update Infrastructure 5 rhui5/cds-rhel9 1791978528, rhui5/rhua-rhel9 1791978693, rhui5/installer-rhel9 1791964013, rhui5/cds-kubernetes-rhel9 1791978534
    fixed: vendor fix RHSA-2026:82939
  • Red Hat Enterprise Linux 6 python, tkinter, python-libs, python-test, python-tools Red Hat Enterprise Linux 7 python, tkinter, python-libs, python-test, python-tools Red Hat Enterprise Linux 8 scipy, python36, python-nose, python-wheel, python3-bson, python3-nose, +19 more Red Hat Update Infrastructure 5 rhui5/haproxy-rhel9 1791978528
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
23 d ago

Exploit prediction

0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 7.6 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
CNA 4.0 7.6 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected packages

ecosystem package affected fixed in
bitnami libpython
<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
3.10.22
3.11.17
3.12.15
3.13.16
3.14.8
bitnami python
<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
3.10.22
3.11.17
3.12.15
3.13.16
3.14.8
bitnami python-min
<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
3.10.22
3.11.17
3.12.15
3.13.16
3.14.8

Affected products

  • Python Software Foundation CPython

Classification

Weakness
  • CWE-297 Improper Validation of Certificate with Host Mismatch

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.