What’s Vulnerable › Vulnerabilities

CVE-2025-8037: Nameless cookies shadow secure cookies

• Severity: critical (CVSS 9.1 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: 2025-07-22 · updated 2026-10-05
• Weakness: CWE-614

Description

Setting a nameless cookie with an equals sign in the value shadowed other cookies. Even if the nameless cookie was set over HTTP and the shadowed cookie included the `Secure` attribute. This vulnerability was fixed in Firefox 141, Firefox ESR 140.1, Thunderbird 141, and Thunderbird 140.1.

Affected products

• Mozilla Firefox: before 140.1; before 141.0 — fixed in 140.1, 141.0
• Mozilla Thunderbird: before 140.1; before 141.0 — fixed in 140.1, 141.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 140.1, 141.0; Mozilla Thunderbird 140.1, 141.0. Check the vendor advisory for mitigations.

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/
• https://www.mozilla.org/security/advisories/mfsa2025-61/
• https://www.mozilla.org/security/advisories/mfsa2025-63/

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