User Cookie Manipulation Issue in Firefox and Thunderbird Software
CVE-2025-8037

9.1CRITICAL

Key Information:

Vendor

Mozilla
Status
Firefox
Firefox Esr
Thunderbird
Vendor
CVE Published:
22 July 2025

What is CVE-2025-8037?

A vulnerability exists in Firefox and Thunderbird that allows an unnamed cookie with an equals sign in its value to shadow other cookies. This can occur even if the shadowed cookies have the 'Secure' attribute set, raising concerns regarding the effectiveness of security measures. This flaw can be exploited in various scenarios, potentially compromising user privacy and data integrity across affected versions of the software.

Affected Version(s)

Firefox < 141

Firefox ESR < 140.1

Thunderbird < 141

References

https://bugzilla.mozilla.org/show_bug.cgi?id=1964767
https://www.mozilla.org/security/advisories/mfsa2025-56/
https://www.mozilla.org/security/advisories/mfsa2025-59/

CVSS V3.1

Score:
9.1
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Uku Sõrmus
.
CVE-2025-8037 : User Cookie Manipulation Issue in Firefox and Thunderbird Software