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High8.8Red Hat Linux

High [CVE-2026-5731] Memory safety bugs fixed in Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2

This high-severity Red Hat Linux advisory covers CVE-2026-5731 affecting Red Hat Enterprise Linux 10.0 Extended Update Support, Red Hat Enterprise Linux 7 Extended Lifecycle Support, Red Hat Enterprise Linux 8.2 Advanced Update Support.

CVE-2026-5731 Published Apr 7, 2026
CVE-2026-5731
Affected products & platforms
Red Hat LinuxUnclassified
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Summary

Memory safety bugs fixed in Firefox ESR 115.34.1, Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2. Red Hat rates this important (CVSS 8.8).

Weakness: CWE-787. Affected package(s): thunderbird, firefox.

Resolved in Red Hat advisory RHSA-2026:11805 — update the affected packages (`sudo dnf update`).

Affected products named by the advisory: Red Hat Enterprise Linux 10.0 Extended Update Support; Red Hat Enterprise Linux 7 Extended Lifecycle Support; Red Hat Enterprise Linux 8.2 Advanced Update Support; Red Hat Enterprise Linux 8.4 Advanced Mission Critical Update Support; and 10 more.

Affected versions
  • thunderbird-0:140.9.1-1.el8_6
  • thunderbird-0:140.9.1-1.el10_0
  • thunderbird-0:140.9.1-1.el9_6
  • thunderbird-0:140.9.1-1.el8_4
  • thunderbird-0:140.9.1-1.el9_4
  • thunderbird-0:140.9.1-1.el9_2
  • thunderbird-0:140.9.1-1.el9_0
  • firefox-0:140.9.1-1.el8_4
  • firefox-0:140.9.1-1.el9_4
  • firefox-0:140.9.1-1.el8_6
  • firefox-0:140.9.1-2.el7_9
  • firefox-0:140.9.1-1.el9_6

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Fixed versions
  • RHSA-2026:11805

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

Mitigation checklist

Recommended fix / mitigation
  • Update the affected package(s) to the fixed version shipped in RHSA-2026:11805 (`sudo dnf update` / `yum update`).

Official advisory · high-confidence parse· fetched 2 months ago·verify at source

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