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CVE-2026-15308VulnerabilityPublished Updated

Red Hat Security Advisory: python3.9 security, bug fix, and enhancement update

Affects Red Hat python3.9 security,Source 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, 01:56 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 python3.9 packages for Red Hat Enterprise Linux 9 and related variants that address this vulnerability. Users should apply the update as described in Red Hat advisory RHSA-2026:39798 to remediate the issue. No additional mitigation steps are indicated by the vendor.

Description

A security advisory from Red Hat addresses a CPU Denial of Service vulnerability in the Python 3.9 HTML parser caused by repeated unterminated markup declarations (CVE-2026-15308). This issue affects Python as packaged in Red Hat Enterprise Linux 9 and related distributions. The advisory also includes bug fixes and enhancements unrelated to the security issue. The vulnerability is rated as having an Important security impact by Red Hat Product Security. Updated packages are available to remediate the issue.

References

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