CVE-2020-26951

critical
Published — · Modified —
CVSS v3
CVSS v2
VIR risk
9.5

Description

A parsing and event loading mismatch in Firefox's SVG code could have allowed load events to fire, even after sanitization. An attacker already capable of exploiting an XSS vulnerability in privileged internal pages could have used this attack to bypass our built-in sanitizer. This vulnerability affects Firefox < 83, Firefox ESR < 78.5, and Thunderbird < 78.5.

Predictions

Exploit likelihood
20%
Patch ETA

Heuristic predictions, AS-IS, for prioritization only.

Mitigations

vendor Authored 2026-05-27

Vendor advisory: debian — https://security-tracker.debian.org/tracker/CVE-2020-26951

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2020-26951.html

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-202011-12

OS impact

OSVersionStatusFixed in
arch archfixed83.0-1
suse slesaffected
debian debiansidfixed83.0-1
debian debianbookwormfixed78.5.0esr-1
debian debianbullseyefixed78.5.0esr-1
debian debianforkyfixed78.5.0esr-1
debian debiantrixiefixed78.5.0esr-1

References

Verify integrity in audit chain (admin only). AS-IS.