CVE-2021-23999

high
Published — · Modified —
CVSS v3
CVSS v2
VIR risk
8.0

Description

If a Blob URL was loaded through some unusual user interaction, it could have been loaded by the System Principal and granted additional privileges that should not be granted to web content. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.

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-2021-23999

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2021-23999.html

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-202104-3

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-202104-4

OS impact

OSVersionStatusFixed in
arch archfixed78.10.0-1
suse slesaffected
debian debiansidfixed88.0-1
debian debianbookwormfixed78.10.0esr-1
debian debianbullseyefixed78.10.0esr-1
debian debianforkyfixed78.10.0esr-1
debian debiantrixiefixed78.10.0esr-1

References

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