What’s Vulnerable › Vulnerabilities

CVE-2023-6204

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2023-11-21 · updated 2026-06-17
• Weakness: CWE-125

Description

On some systems—depending on the graphics settings and drivers—it was possible to force an out-of-bounds read and leak memory data into the images created on the canvas element. This vulnerability affects Firefox < 120, Firefox ESR < 115.5.0, and Thunderbird < 115.5.

Affected products

• Debian Linux: 10.0, 11.0, 12.0
• Mozilla Firefox: before 120.0 — fixed in 120.0
• Mozilla Firefox ESR: before 115.5.0 — fixed in 115.5.0
• Mozilla Thunderbird: before 115.5 — fixed in 115.5

How to fix

Upgrade to a fixed version: Mozilla Firefox 120.0; Mozilla Firefox ESR 115.5.0; Mozilla Thunderbird 115.5. Check the vendor advisory for mitigations.

References

• https://bugzilla.mozilla.org/show_bug.cgi?id=1841050
• https://lists.debian.org/debian-lts-announce/2023/11/msg00017.html
• https://lists.debian.org/debian-lts-announce/2023/11/msg00030.html
• https://www.debian.org/security/2023/dsa-5561
• https://www.mozilla.org/security/advisories/mfsa2023-49/
• https://www.mozilla.org/security/advisories/mfsa2023-50/
• https://www.mozilla.org/security/advisories/mfsa2023-52/
• https://bugzilla.mozilla.org/show_bug.cgi?id=1841050
• https://lists.debian.org/debian-lts-announce/2023/11/msg00017.html
• https://lists.debian.org/debian-lts-announce/2023/11/msg00030.html
• https://www.debian.org/security/2023/dsa-5561
• https://www.mozilla.org/security/advisories/mfsa2023-49/

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