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CVE-2026-15308VulnerabilityPublished Updated

Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update

Affects Red HatSource 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, 02:05 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 updated python3.14 RPM packages (version 3.14.6-1.3.hum1) that fix this vulnerability. Users should apply these updates to mitigate the issue. No other mitigations are currently available or meet Red Hat's criteria for ease of use and applicability. Refer to the Red Hat advisory (https://access.redhat.com/errata/RHSA-2026:37533) for update instructions.

Description

A vulnerability in Python's html.parser.HTMLParser allows a remote attacker to cause a denial of service by sending specially crafted malformed HTML with repeated unterminated markup declarations. This leads to excessive CPU consumption and makes the affected system unresponsive. The issue affects Red Hat Hardened Images RPMs that include python3.14 components. Red Hat has released updated RPM packages to address this vulnerability.

References

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