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Vulnerability record · CVE-2023-6856 · published 19 December 2023

CVE-2023-6856: Mozilla firefox out-of-bounds write vulnerability

Mozilla · Firefox

The WebGL `DrawElementsInstanced` method was susceptible to a heap buffer overflow when used on systems with the Mesa VM driver. This issue could allow an attacker to perform remote code execution and sandbox escape. This vulnerability affects Firefox ESR < 115.6, Thunderbird < 115.6, and Firefox < 121.

8.8 CVSS 3.1 High EPSS 21% · top 2.6% CWE-787 · Out-of-bounds write
8.8CVSS 3.1 base score
21%EPSS exploitation probability, 30 days
NoNot in CISA KEV
4Affected product versions listed by NVD
18References
17 Jun 2026Last modified by NVD

Description

The WebGL `DrawElementsInstanced` method was susceptible to a heap buffer overflow when used on systems with the Mesa VM driver. This issue could allow an attacker to perform remote code execution and sandbox escape. This vulnerability affects Firefox ESR < 115.6, Thunderbird < 115.6, and Firefox < 121.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

4 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://bugzilla.mozilla.org/show_bug.cgi?id=1843782 Issue TrackingPermissions Required
https://lists.debian.org/debian-lts-announce/2023/12/msg00020.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2023/12/msg00021.html Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202401-10 Third Party Advisory
https://www.debian.org/security/2023/dsa-5581 Third Party Advisory
https://www.debian.org/security/2023/dsa-5582 Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2023-54/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2023-55/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2023-56/ Vendor Advisory
https://bugzilla.mozilla.org/show_bug.cgi?id=1843782 Issue TrackingPermissions Required
https://lists.debian.org/debian-lts-announce/2023/12/msg00020.html Mailing ListThird Party Advisory
https://lists.debian.org/debian-lts-announce/2023/12/msg00021.html Mailing ListThird Party Advisory
https://security.gentoo.org/glsa/202401-10 Third Party Advisory
https://www.debian.org/security/2023/dsa-5581 Third Party Advisory
https://www.debian.org/security/2023/dsa-5582 Third Party Advisory
https://www.mozilla.org/security/advisories/mfsa2023-54/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2023-55/ Vendor Advisory
https://www.mozilla.org/security/advisories/mfsa2023-56/ Vendor Advisory

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Source: NIST National Vulnerability Database (record CVE-2023-6856), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.