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CVE-2026-0865VulnerabilityPublished Updated

Red Hat Security Advisory: python3.9 security update

Affects Red Hat python3.9Source GCVE Database

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Authoritative record:CVE-2026-0865· Medium 5.9

Not known to be exploited · CVSS 5.9 Medium · fixed in Red Hat package updates : update Red Hat cpython when convenient.

Data as of 5 Nov 2026, 18:05 UTC

CVSS 4.0 base score
5.9Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 3.15.0a6, 3.14.3, 3.13.12 +3
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 20 Jan 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 5 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
Python Software FoundationCPythonAffected
  • >=3.15.0a1 <3.15.0a6
Fixed in
  • 3.15.0a6
Python Software FoundationCPythonAffected
  • >=3.14.0 <3.14.3
Fixed in
  • 3.14.3
Python Software FoundationCPythonAffected
  • >=3.13.0 <3.13.12
Fixed in
  • 3.13.12
Python Software FoundationCPythonAffected
  • >=3.12.0 <3.12.13
Fixed in
  • 3.12.13
Python Software FoundationCPythonAffected
  • >=3.11.0 <3.11.15
Fixed in
  • 3.11.15
Python Software FoundationCPythonAffected
  • <3.10.20
Fixed in
  • 3.10.20

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 that fix this vulnerability. Users should apply the official Red Hat security update RHSA-2026:18693 to remediate this issue. For detailed update instructions, refer to Red Hat's article at https://access.redhat.com/articles/11258. No additional mitigation steps are indicated by the vendor.

Description

A security update for python3.9 in Red Hat Enterprise Linux 9 addresses a vulnerability in the cpython wsgiref.headers.Headers module that allows header newline injection (CVE-2026-0865). This issue could potentially allow injection of newline characters into HTTP headers, which may lead to security risks. Red Hat has rated this update as having a moderate security impact and has released updated packages to fix the issue.

References

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