What’s Vulnerable › Vulnerabilities

CVE-2025-4087: Unsafe attribute access during XPath parsing

• Severity: medium (CVSS 4.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-04-29 · updated 2026-10-05
• Weakness: CWE-125

Description

A vulnerability was identified in Thunderbird where XPath parsing could trigger undefined behavior due to missing null checks during attribute access. This could lead to out-of-bounds read access and potentially, memory corruption. This vulnerability was fixed in Firefox 138, Firefox ESR 128.10, Thunderbird 138, and Thunderbird 128.10.

Affected products

• Mozilla Firefox: before 128.10; before 138.0 — fixed in 128.10, 138.0
• Mozilla Thunderbird: before 128.10.0; before 138.0 — fixed in 128.10.0, 138.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 128.10, 138.0; Mozilla Thunderbird 128.10.0, 138.0. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1952465
• https://www.mozilla.org/security/advisories/mfsa2025-28/
• https://www.mozilla.org/security/advisories/mfsa2025-29/
• https://www.mozilla.org/security/advisories/mfsa2025-31/
• https://www.mozilla.org/security/advisories/mfsa2025-32/
• https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html

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