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CVE-2026-15308VulnerabilityPublished Updated

Red Hat Security Advisory: python3.12 security update

Affects Red Hat python3.12Source GCVE Database

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Authoritative record:CVE-2026-15308· High 8.7

Not known to be exploited · CVSS 8.7 High · fixed in Red Hat package updates : patch Red Hat CPython soon.

Data as of 1 Nov 2026, 01:55 UTC

CVSS 4.0 base score
8.7High
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 3.15.0b4, 3.14.7, 3.13.15 +3
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 31 Oct 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Python Software FoundationCPythonAffected
  • >=3.15.0a1 <3.15.0b4
Fixed in
  • 3.15.0b4
Python Software FoundationCPythonAffected
  • >=3.14.0 <3.14.7
Fixed in
  • 3.14.7
Python Software FoundationCPythonAffected
  • >=3.13.0 <3.13.15
Fixed in
  • 3.13.15
Python Software FoundationCPythonAffected
  • >=3.12.0 <3.12.14
Fixed in
  • 3.12.14
Python Software FoundationCPythonAffected
  • >=3.11.0 <3.11.16
Fixed in
  • 3.11.16
Python Software FoundationCPythonAffected
  • <3.10.21
Fixed in
  • 3.10.21

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Red Hat has released an updated python3.12 package (version 3.12.9-1.el9_6.9) that fixes this vulnerability. Users of Red Hat Enterprise Linux 9.6 Extended Update Support and related variants should apply the security update as described in the Red Hat advisory (https://access.redhat.com/articles/11258). No additional mitigation steps are indicated.

Description

A denial of service vulnerability (CVE-2026-15308) exists in the Python 3.12 HTML parser due to repeated unterminated markup declarations. This flaw can cause excessive CPU consumption, leading to a denial of service condition. Red Hat has issued a security update for python3.12 in Red Hat Enterprise Linux 9.6 Extended Update Support to address this issue.

References

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