What’s Vulnerable › Vulnerabilities

CVE-2023-6857

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.7% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-12-19 · updated 2026-06-17
• Weakness: CWE-362

Description

When resolving a symlink, a race may occur where the buffer passed to `readlink` may actually be smaller than necessary. *This bug only affects Firefox on Unix-based operating systems (Android, Linux, MacOS). Windows is unaffected.* This vulnerability affects Firefox ESR < 115.6, Thunderbird < 115.6, and Firefox < 121.

Affected products

• Debian Linux: 10.0, 11.0, 12.0
• Mozilla Firefox: before 121.0 — fixed in 121.0
• Mozilla Firefox ESR: before 115.6 — fixed in 115.6
• Mozilla Thunderbird: before 115.6 — fixed in 115.6

How to fix

Upgrade to a fixed version: Mozilla Firefox 121.0; Mozilla Firefox ESR 115.6; Mozilla Thunderbird 115.6. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1796023
• https://lists.debian.org/debian-lts-announce/2023/12/msg00020.html
• https://lists.debian.org/debian-lts-announce/2023/12/msg00021.html
• https://security.gentoo.org/glsa/202401-10
• https://www.debian.org/security/2023/dsa-5581
• https://www.debian.org/security/2023/dsa-5582
• https://www.mozilla.org/security/advisories/mfsa2023-54/
• https://www.mozilla.org/security/advisories/mfsa2023-55/
• https://www.mozilla.org/security/advisories/mfsa2023-56/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1796023
• https://lists.debian.org/debian-lts-announce/2023/12/msg00020.html
• https://lists.debian.org/debian-lts-announce/2023/12/msg00021.html

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