CVE-2023-6857

MEDIUM 5.3CVE-2023-6857 · Published 19/12/2023 · updated 17/06/2026

In short

CVE-2023-6857 is a MEDIUM (CVSS 5.3) vulnerability affecting firefox (mozilla), firefox esr (mozilla), thunderbird (mozilla).
Chance of exploitation in the next 30 days (EPSS): 0.66%, higher than 51.8% of all vulnerabilities.
Fix: update to 121.0, 115.6 or later.

Package	Affected versions	Patched versions
firefox mozilla	`< 121.0`	`121.0`
firefox esr mozilla	`< 115.6`	`115.6`
thunderbird mozilla	`< 115.6`	`115.6`

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.

References

bugzilla.mozilla.org/show_bug.cgi · Issue Tracking
lists.debian.org/debian-lts-announce/2023/12/msg00020.html · Mailing List
lists.debian.org/debian-lts-announce/2023/12/msg00021.html · Mailing List
security.gentoo.org/glsa/202401-10 · Third Party Advisory
debian.org/security/2023/dsa-5581 · Third Party Advisory
debian.org/security/2023/dsa-5582 · Third Party Advisory
mozilla.org/security/advisories/mfsa2023-54 · Vendor Advisory
mozilla.org/security/advisories/mfsa2023-55 · Vendor Advisory
mozilla.org/security/advisories/mfsa2023-56 · Vendor Advisory

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Package

Affected versions

Patched versions

firefox

mozilla

< 121.0

121.0

firefox esr

mozilla

< 115.6

115.6

thunderbird

mozilla

< 115.6

115.6

Description

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