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VulnerabilityPublished Updated

CVE-2025-4087: Firefox · Out-of-bounds Read

Source GCVE Database

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Not known to be exploited · CVSS 6.5 Medium · fixed in 138 : update affected systems when convenient.

Data as of 30 Oct 2026, 01:34 UTC

CVSS 3.1 base score
6.5Medium
How severe the flaw is on the 0–10 CVSS scale.
Patch
Available – fixed in 138, 128.10
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Apr 2025

  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 29 Oct 2026.

What to do

AI-suggested

Mozilla has released official fixes for this vulnerability in Firefox 138, Firefox ESR 128.10, Thunderbird 138, and Thunderbird ESR 128.10. Users and administrators should update to these versions or later to remediate the issue. No additional mitigations are required once the update is applied.

Description

A vulnerability in Firefox's XPath parsing component could cause undefined behavior due to missing null checks during attribute access. This flaw may lead to out-of-bounds read access and potential memory corruption. The issue affects Firefox versions prior to 138, Firefox ESR versions prior to 128.10, Thunderbird versions prior to 138, and Thunderbird ESR versions prior to 128.10. Mozilla has addressed this vulnerability in Firefox 138 and Firefox ESR 128.10.

References

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