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CVE-2025-4087

Unsafe attribute access during XPath parsing

MEDIUM
4.8
CVSS Score
Published: April 29, 2025 at 01:13 PM UTC
Updated: October 5, 2026 at 03:10 PM UTC
2 products affected across 1 vendorFirefoxThunderbird

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Severity
MEDIUM4.8
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

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 affects Firefox < 138, Firefox ESR < 128.10, Thunderbird < 138, and Thunderbird < 128.10.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Firefox· Mozilla
95%
v < 128.10v < 138.0
Vendor states this is fixed in 128.10 (unaffected)
Vendor states this is fixed in 138 (unaffected)
Affected range stops below 138.0, so it looks safe — our inference, not a vendor statement
Thunderbird· Mozilla
95%
v < 128.10.0v < 138.0
Vendor states this is fixed in 128.10 (unaffected)
Affected range stops below 128.10.0, so it looks safe — our inference, not a vendor statement
Vendor states this is fixed in 138 (unaffected)
Affected range stops below 138.0, so it looks safe — our inference, not a vendor statement

References (6)

Permissions Required
Source: [email protected]
https://bugzilla.mozilla.org/show_bug.cgi?id=1952465
Vendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2025-28/
Vendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2025-29/
Vendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2025-31/
Vendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2025-32/
Source: af854a3a-2127-422b-91ae-364da2661108
https://lists.debian.org/debian-lts-announce/2025/05/msg00024.html

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.8MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-125

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