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Fencer Vulns
high 7.5

CVE-2026-15308 json

Incremental HTMLParser feed() allows CPU-exhaustion DoS via repeated unterminated markup declarations

published 2026-07-09 4 mo ago modified 2026-10-25 14 d ago also BIT-libpython-2026-15308 , BIT-python-2026-15308 , BIT-python-min-2026-15308 , EUVD-2026-42638

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

The incremental HTML parser (html.parser.HTMLParser) allows for CPU denial-of-service through repeated unterminated markup declarations when processing uncontrolled data.

Patch / fix

  • bitnami libpython 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7
  • bitnami python 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7
  • bitnami python-min 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7
  • Python Software Foundation CPython 3.10.21, 3.11.16, 3.12.14, 3.13.15, 3.14.7, 3.15.0b4
  • python3.11 Debian 12 3.11.2-6+deb12u9
  • python3.14 Debian 14 3.14.7-1

debian advisories DEBIAN-CVE-2026-15308

  • python3.10 Ubuntu 22.04 LTS 3.10.12-1~22.04.18
  • python3.12 Ubuntu 24.04 LTS 3.12.3-1ubuntu0.17
  • python3.14 Ubuntu 26.04 LTS 3.14.4-1ubuntu0.2
  • python2.7 Ubuntu Pro 14.04 LTS 2.7.6-8ubuntu0.6+esm30
  • python2.7 Ubuntu Pro 16.04 LTS 2.7.12-1ubuntu0~16.04.18+esm22
  • python2.7 Ubuntu Pro 18.04 LTS 2.7.17-1~18.04ubuntu1.13+esm15
  • python2.7 Ubuntu Pro 22.04 LTS 2.7.18-13ubuntu1.5+esm9
  • python3.4 Ubuntu Pro 14.04 LTS 3.4.3-1ubuntu1~14.04.7+esm21

ubuntu advisories UBUNTU-CVE-2026-15308

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • python3.13 hummingbird 1 3.13.15-1.hum1
  • python3.13-idle hummingbird 1 3.13.15-1.hum1
  • python3.13-libs hummingbird 1 3.13.15-1.hum1
  • python3.13-test hummingbird 1 3.13.15-1.hum1
  • python3.13-tkinter hummingbird 1 3.13.15-1.hum1
  • python3.13-freethreading hummingbird 1 3.13.15-1.hum1
  • python3 hummingbird 1 3.14.7-1.hum1
  • python3.14 hummingbird 1 3.14.7-1.hum1

red hat advisories RHSA-2026:76945RHSA-2026:74088RHSA-2026:74087RHSA-2026:54554RHSA-2026:54534RHSA-2026:50816

  • python3 SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +11 more 3.6.15-150300.10.129.1
  • python3-core SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +12 more 3.6.15-150300.10.129.1
  • grafana Multi Linux Manager Tools SLE-15 12.4.10-150002.4.27.1
  • mgr-push Multi Linux Manager Tools SLE-15 5.2.5-150002.3.12.1
  • spacecmd Multi Linux Manager Tools SLE-15 5.2.10-150002.3.15.1
  • uyuni-tools Multi Linux Manager Tools SLE-Micro-5, Multi Linux Manager Tools SLE-15 5.2.17-150002.3.20.1
  • venv-salt-minion Multi Linux Manager Tools SLE-Micro-5, Multi Linux Manager Tools SLE-15 3006.0-150002.5.22.1
  • spacewalk-client-tools Multi Linux Manager Tools SLE-15 5.2.7-150002.3.12.1

suse advisories SUSE-SU-2026:4754-1SUSE-SU-2026:4585-1SUSE-SU-2026:4584-1SUSE-SU-2026:4583-1SUSE-SU-2026:4582-1SUSE-SU-2026:4581-1

  • python314 openSUSE Tumbleweed 3.14.7-1.1
  • python313 openSUSE Leap 16.0 3.13.14-160000.2.1
  • python313-core openSUSE Leap 16.0 3.13.14-160000.2.1
  • python313-nogil openSUSE Leap 16.0 3.13.14-160000.2.1
  • python313-documentation openSUSE Leap 16.0 3.13.14-160000.2.1
  • python313-nogil-nogil-core openSUSE Leap 16.0 3.13.14-160000.2.1
  • python313 openSUSE Tumbleweed 3.13.14-2.1
  • python310 openSUSE Tumbleweed 3.10.20-8.1

opensuse advisories openSUSE-SU-2026:11597-1openSUSE-SU-2026:21595-1openSUSE-SU-2026:11534-1openSUSE-SU-2026:11426-1openSUSE-SU-2026:11427-1openSUSE-SU-2026:11428-1

  • python3.14 AlmaLinux 9 3.14.5-1.el9_8.1
  • python3.14-idle AlmaLinux 9 3.14.5-1.el9_8.1
  • python3.14-libs AlmaLinux 9 3.14.5-1.el9_8.1
  • python3.14-test AlmaLinux 9 3.14.5-1.el9_8.1
  • python3.14-tkinter AlmaLinux 9 3.14.5-1.el9_8.1
  • python3.14-freethreading AlmaLinux 9 3.14.5-1.el9_8.1
  • python3.14-freethreading-idle AlmaLinux 9 3.14.5-1.el9_8.1
  • python3.14-freethreading-libs AlmaLinux 9 3.14.5-1.el9_8.1

almalinux advisories ALSA-2026:41949ALSA-2026:40856ALSA-2026:39771ALSA-2026:39798ALSA-2026:39893ALSA-2026:39183

  • python3.14 Rocky Linux 10 3.14.5-1.el10_2.1
  • python3.14 Rocky Linux 9 3.14.5-1.el9_8.1
  • python3.12 Rocky Linux 9 3.12.13-3.el9_8.1
  • python3.9 Rocky Linux 9 3.9.25-7.el9_8.2
  • python3.12 Rocky Linux 8 3.12.13-3.el8_10
  • python3.12 Rocky Linux 10 3.12.13-2.el10_2.1
  • python3 Rocky Linux 8 3.6.8-77.el8_10.rocky.0

rocky linux advisories RLSA-2026:40856RLSA-2026:41949RLSA-2026:39771RLSA-2026:39798RLSA-2026:39893RLSA-2026:39183

  • python3 Alpine 3.23, Alpine 3.22, Alpine 3.21 3.12.14-r0
  • python3 Alpine 3.24 3.14.7-r0

alpine advisories ALPINE-CVE-2026-15308

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

  • python3 Azure Linux 3.0 3.12.14-1

azure linux advisories AZL-92271

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

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-2026-15308 updated cvss 7.5

python: Python: CPU Denial of Service in HTML parser via repeated unterminated markup declarations

  • Red Hat Exploit Intelligence exploit-intelligence-tech-preview/vulnerability-analysis-rhel9
    affected: workaround, no fix available
  • Red Hat Enterprise Linux 6 python, tkinter, python-libs, python-test, python-tools Red Hat Enterprise Linux 7 python, python3, tkinter, python-libs, python-test, python-tools, +4 more
    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 Self-service automation portal 2 ansible-automation-platform/bootc-automation-portal-rhel9
    affected: workaround, no fix available
  • Red Hat CodeReady Linux Builder EUS (v.9.6) python3 3.9.21-2.el9_6.7, python3.12 3.12.9-1.el9_6.9, python3-idle 3.9.21-2.el9_6.7, python3-test 3.9.21-2.el9_6.7, python3-tkinter 3.9.21-2.el9_6.7, python3.12-idle 3.12.9-1.el9_6.9, +2 more
    fixed: vendor fix RHSA-2026:74088
  • Red Hat Discovery 2 discovery/discovery-ui-rhel9 1784821750, discovery/discovery-server-rhel9 1784821670
    fixed: vendor fix RHSA-2026:46836
  • Red Hat Enterprise Linux AppStream (v. 8) python3.12 3.12.13-3.el8_10, python3-idle 3.6.8-77.el8_10, python3-test 3.6.8-77.el8_10, platform-python 3.6.8-77.el8_10, python3-tkinter 3.6.8-77.el8_10, python3.12-libs 3.12.13-3.el8_10, +2 more
    fixed: vendor fix RHSA-2026:39320
  • Red Hat Enterprise Linux AppStream (v. 9) python3.14 3.14.5-1.el9_8.1, python3.12 3.12.13-3.el9_8.1, python3-tkinter 3.9.25-7.el9_8.2, python3.14-libs 3.14.5-1.el9_8.1, python3.12-libs 3.12.13-3.el9_8.1, python3.14-tkinter 3.14.5-1.el9_8.1, +2 more
    fixed: vendor fix RHSA-2026:39798
show 31 more
  • Red Hat Enterprise Linux AppStream (v. 10) python3.14 3.14.5-1.el10_2.1, python3.14-libs 3.14.5-1.el10_2.1, python3-tkinter 3.12.13-2.el10_2.1, python3.14-tkinter 3.14.5-1.el10_2.1, python-unversioned-command 3.12.13-2.el10_2.1
    fixed: vendor fix RHSA-2026:39183
  • Red Hat Enterprise Linux AppStream AUS (v.8.4) python3-idle 3.6.8-39.el8_4.12, python3-test 3.6.8-39.el8_4.12, platform-python 3.6.8-39.el8_4.12, python3-tkinter 3.6.8-39.el8_4.12
    fixed: vendor fix RHSA-2026:50816
  • Red Hat Enterprise Linux AppStream AUS (v.8.6) python3-idle 3.6.8-47.el8_6.14, python3-test 3.6.8-47.el8_6.14, platform-python 3.6.8-47.el8_6.14, python3-tkinter 3.6.8-47.el8_6.14
    fixed: vendor fix RHSA-2026:50065
  • Red Hat Enterprise Linux AppStream E4S (v.8.8) python3-idle 3.6.8-51.el8_8.16, python3-test 3.6.8-51.el8_8.16, platform-python 3.6.8-51.el8_8.16, python3-tkinter 3.6.8-51.el8_8.16
    fixed: vendor fix RHSA-2026:50064
  • Red Hat Enterprise Linux AppStream E4S (v.9.2) python3-tkinter 3.9.16-1.el9_2.15, python-unversioned-command 3.9.16-1.el9_2.15
    fixed: vendor fix RHSA-2026:76945
  • Red Hat Enterprise Linux AppStream E4S (v.9.4) python3.12 3.12.1-4.el9_4.14, python3-tkinter 3.9.18-3.el9_4.14, python3.12-libs 3.12.1-4.el9_4.14, python3.12-tkinter 3.12.1-4.el9_4.14, python-unversioned-command 3.9.18-3.el9_4.14
    fixed: vendor fix RHSA-2026:74087
  • Red Hat Enterprise Linux AppStream EUS (v. 10.0) python3-tkinter 3.12.9-2.el10_0.10, python-unversioned-command 3.12.9-2.el10_0.10
    fixed: vendor fix RHSA-2026:47939
  • Red Hat Enterprise Linux AppStream EUS (v.9.6) python3.12 3.12.9-1.el9_6.9, python3-tkinter 3.9.21-2.el9_6.7, python3.12-libs 3.12.9-1.el9_6.9, python3.12-tkinter 3.12.9-1.el9_6.9, python-unversioned-command 3.9.21-2.el9_6.7
    fixed: vendor fix RHSA-2026:74088
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.4) python3-idle 3.6.8-39.el8_4.12, python3-test 3.6.8-39.el8_4.12, platform-python 3.6.8-39.el8_4.12, python3-tkinter 3.6.8-39.el8_4.12
    fixed: vendor fix RHSA-2026:50816
  • Red Hat Enterprise Linux AppStream EUS EXTENSION (v.8.6) python3-idle 3.6.8-47.el8_6.14, python3-test 3.6.8-47.el8_6.14, platform-python 3.6.8-47.el8_6.14, python3-tkinter 3.6.8-47.el8_6.14
    fixed: vendor fix RHSA-2026:50065
  • Red Hat Enterprise Linux AppStream TUS (v.8.8) python3-idle 3.6.8-51.el8_8.16, python3-test 3.6.8-51.el8_8.16, platform-python 3.6.8-51.el8_8.16, python3-tkinter 3.6.8-51.el8_8.16
    fixed: vendor fix RHSA-2026:50064
  • Red Hat Enterprise Linux BaseOS (v. 8) python3 3.6.8-77.el8_10, python3-libs 3.6.8-77.el8_10, python3-test 3.6.8-77.el8_10, platform-python 3.6.8-77.el8_10
    fixed: vendor fix RHSA-2026:39320
  • Red Hat Enterprise Linux BaseOS (v. 9) python3 3.9.25-7.el9_8.2, python3.9 3.9.25-7.el9_8.2, python3-libs 3.9.25-7.el9_8.2
    fixed: vendor fix RHSA-2026:39798
  • Red Hat Enterprise Linux BaseOS (v. 10) python3 3.12.13-2.el10_2.1, python3.12 3.12.13-2.el10_2.1, python3-libs 3.12.13-2.el10_2.1
    fixed: vendor fix RHSA-2026:39183
  • Red Hat Enterprise Linux BaseOS AUS (v.8.4) python3 3.6.8-39.el8_4.12, python3-libs 3.6.8-39.el8_4.12, python3-test 3.6.8-39.el8_4.12, platform-python 3.6.8-39.el8_4.12
    fixed: vendor fix RHSA-2026:50816
  • Red Hat Enterprise Linux BaseOS AUS (v.8.6) python3 3.6.8-47.el8_6.14, python3-libs 3.6.8-47.el8_6.14, python3-test 3.6.8-47.el8_6.14, platform-python 3.6.8-47.el8_6.14
    fixed: vendor fix RHSA-2026:50065
  • Red Hat Enterprise Linux BaseOS E4S (v.8.8) python3 3.6.8-51.el8_8.16, python3-libs 3.6.8-51.el8_8.16, python3-test 3.6.8-51.el8_8.16, platform-python 3.6.8-51.el8_8.16
    fixed: vendor fix RHSA-2026:50064
  • Red Hat Enterprise Linux BaseOS E4S (v.9.2) python3 3.9.16-1.el9_2.15, python3.9 3.9.16-1.el9_2.15, python3-libs 3.9.16-1.el9_2.15
    fixed: vendor fix RHSA-2026:76945
  • Red Hat Enterprise Linux BaseOS E4S (v.9.4) python3 3.9.18-3.el9_4.14, python3.9 3.9.18-3.el9_4.14, python3-libs 3.9.18-3.el9_4.14
    fixed: vendor fix RHSA-2026:74087
  • Red Hat Enterprise Linux BaseOS EUS (v. 10.0) python3 3.12.9-2.el10_0.10, python3.12 3.12.9-2.el10_0.10, python3-libs 3.12.9-2.el10_0.10
    fixed: vendor fix RHSA-2026:47939
  • Red Hat Enterprise Linux BaseOS EUS (v.9.6) python3 3.9.21-2.el9_6.7, python3.9 3.9.21-2.el9_6.7, python3-libs 3.9.21-2.el9_6.7
    fixed: vendor fix RHSA-2026:74088
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.4) python3 3.6.8-39.el8_4.12, python3-libs 3.6.8-39.el8_4.12, python3-test 3.6.8-39.el8_4.12, platform-python 3.6.8-39.el8_4.12
    fixed: vendor fix RHSA-2026:50816
  • Red Hat Enterprise Linux BaseOS EUS EXTENSION (v.8.6) python3 3.6.8-47.el8_6.14, python3-libs 3.6.8-47.el8_6.14, python3-test 3.6.8-47.el8_6.14, platform-python 3.6.8-47.el8_6.14
    fixed: vendor fix RHSA-2026:50065
  • Red Hat Enterprise Linux BaseOS TUS (v.8.8) python3 3.6.8-51.el8_8.16, python3-libs 3.6.8-51.el8_8.16, python3-test 3.6.8-51.el8_8.16, platform-python 3.6.8-51.el8_8.16
    fixed: vendor fix RHSA-2026:50064
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 9) python3 3.9.25-7.el9_8.2, python3.14 3.14.5-1.el9_8.1, python3.12 3.12.13-3.el9_8.1, python3-idle 3.9.25-7.el9_8.2, python3-test 3.9.25-7.el9_8.2, python3-tkinter 3.9.25-7.el9_8.2, +11 more
    fixed: vendor fix RHSA-2026:39798
  • Red Hat Enterprise Linux CodeReady Linux Builder (v. 10) python3-idle 3.12.13-2.el10_2.1, python3-test 3.12.13-2.el10_2.1, python3.14-idle 3.14.5-1.el10_2.1, python3.14-test 3.14.5-1.el10_2.1, python3.14-freethreading 3.14.5-1.el10_2.1, python3.14-freethreading-idle 3.14.5-1.el10_2.1, +3 more
    fixed: vendor fix RHSA-2026:39183
  • Red Hat Enterprise Linux CodeReady Linux Builder EUS (v. 10.0) python3-idle 3.12.9-2.el10_0.10, python3-test 3.12.9-2.el10_0.10
    fixed: vendor fix RHSA-2026:47939
  • Red Hat Enterprise Linux CRB (v. 8) python3.12 3.12.13-3.el8_10, python3.12-idle 3.12.13-3.el8_10, python3.12-test 3.12.13-3.el8_10, python3.12-tkinter 3.12.13-3.el8_10
    fixed: vendor fix RHSA-2026:39893
  • Red Hat Hardened Images python3 3.14.7-1.hum1, python3.14 3.14.7-1.hum1, python3.13 3.13.15-1.hum1, python3-idle 3.14.7-1.hum1, python3-libs 3.14.7-1.hum1, python3-test 3.14.7-1.hum1, +38 more
    fixed: vendor fix RHSA-2026:54534
  • Red Hat OpenShift AI 3.0 rhai/base-image-cpu-rhel9 1790277045, rhai/base-image-cpu-rhel9 1791232023, rhai/base-image-tpu-rhel9 1790276884, rhai/base-image-tpu-rhel9 1791232104, rhai/base-image-cuda-rhel9 1790276974, rhai/base-image-cuda-rhel9 1791231840, +4 more
    fixed: vendor fix RHSA-2026:73960
  • Red Hat OpenShift AI 3.2 rhai/base-image-cpu-rhel9 1790703590, rhai/base-image-cpu-rhel9 1791232203, rhai/base-image-tpu-rhel9 1790703497, rhai/base-image-tpu-rhel9 1791231896, rhai/base-image-cuda-rhel9 1790703586, rhai/base-image-cuda-rhel9 1791232024, +6 more
    fixed: vendor fix RHSA-2026:74460

4 more fixed, 3 more not affected in the full advisory

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
yes
Technical impact
partial
Assessed
4 mo ago

Exploit prediction

0.64% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
CNA 4.0 8.7 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami libpython
<3.10.21
>=3.11.0, <3.11.16
>=3.12.0, <3.12.14
>=3.13.0, <3.13.15
>=3.14.0, <3.14.7
3.10.21
3.11.16
3.12.14
3.13.15
3.14.7
bitnami python
<3.10.21
>=3.11.0, <3.11.16
>=3.12.0, <3.12.14
>=3.13.0, <3.13.15
>=3.14.0, <3.14.7
3.10.21
3.11.16
3.12.14
3.13.15
3.14.7
bitnami python-min
<3.10.21
>=3.11.0, <3.11.16
>=3.12.0, <3.12.14
>=3.13.0, <3.13.15
>=3.14.0, <3.14.7
3.10.21
3.11.16
3.12.14
3.13.15
3.14.7

Affected products

  • Python Software Foundation CPython

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

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: NVD does not account for latest released backported remediations.