What is CVE-2024-5699?

CVE-2024-5699 is a critical-severity vulnerability in Mozilla Firefox, classified under Improper Handling of Case Sensitivity. CVSS score: 9.8/10. Published 2024-06-11.

How severe is CVE-2024-5699?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Mozilla Firefox

CVE-2024-5699

In violation of spec, cookie prefixes such as `__Secure` were being ignored if they were not correctly capitalized - by spec they should be checked with a case-insensitive comparison. This could have resulted in the browser not correctly honoring the behaviors specified by the prefix. This vulnerability affects Firefox < 127.

Published 2024-06-11 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.008 (54.2th percentile), scored 2026-10-06.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 54th percentile — 54.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Mozilla Firefox — versions unspecified

Weakness classification (CWE)

CWE-178 — Improper Handling of Case Sensitivity

References

bugzilla.mozilla.org/show_bug.cgi (Exploit, Issue Tracking)
www.mozilla.org/security/advisories/mfsa2024-25/ (Vendor Advisory)

Frequently asked questions

What is CVE-2024-5699?: CVE-2024-5699 is a critical-severity vulnerability in Mozilla Firefox, classified under Improper Handling of Case Sensitivity. CVSS score: 9.8/10. Published 2024-06-11.
How severe is CVE-2024-5699?: Critical severity. CVSS v3 base score is 9.8 out of 10.