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CVE-2026-5731VulnerabilityPublished Updated

Red Hat Security Advisory: thunderbird security update

Affects Red Hat thunderbirdSource GCVE Database

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Mentioned vulnerabilities

Authoritative record:CVE-2026-5731· Critical 9.8

Not known to be exploited · CVSS 9.8 Critical · fixed in Red Hat package updates : patch Red Hat thunderbird as a priority.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 27% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 115.34.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 7 Apr 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 30 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Red Hat Product Security Red HatAffected
  • =115.34.0
  • =140.9.0
  • =149.0.1
Fixed in–

AI-suggested

Red Hat has released updated Thunderbird packages for Red Hat Enterprise Linux 8.4 that address these vulnerabilities. Users should apply the security update as described in the Red Hat advisory RHSA-2026:14303 and the referenced article https://access.redhat.com/articles/11258. No additional mitigations are specified or required beyond applying the official update.

Description

This update for MozillaFirefox fixes the following issues: Update to Firefox Extended Support Release 140.9.1 ESR (bsc#1261663). - MFSA 2026-27: * 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. * CVE-2026-5732: incorrect boundary conditions, integer overflow in the Graphics: Text component. * CVE-2026-5734: memory safety bugs fixed in Firefox ESR 140.9.1, Thunderbird ESR 140.9.1, Firefox 149.0.2 and Thunderbird 149.0.2.

References

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