Cross-Origin Resource Information Leak in Firefox Browser
CVE-2025-5266

4.3MEDIUM

Key Information:

Vendor

Mozilla
Status
Firefox
Firefox Esr
Thunderbird
Vendor
CVE Published:
27 May 2025

What is CVE-2025-5266?

A vulnerability in the Firefox browser and its Extended Support Release allows script elements loading cross-origin resources to generate load and error events, potentially exposing sensitive information. This issue can be exploited through XS-Leaks attacks, where an attacker can infer the existence or status of certain resources through observable side effects. It is critical for users to update to the latest versions of Firefox to mitigate these risks and enhance their security.

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Affected Version(s)

Firefox < 139

Firefox ESR < 128.11

Thunderbird < 139

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1965628
https://www.mozilla.org/security/advisories/mfsa2025-42/
https://www.mozilla.org/security/advisories/mfsa2025-44/

CVSS V3.1

Score:
4.3
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
None
Availability:
Low
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
Required
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Jakub Szymsza
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