CVE-2020-26956

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

Description

In some cases, removing HTML elements during sanitization would keep existing SVG event handlers and therefore lead to XSS. 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-2020-26956

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2020-26956.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.