CVE-2021-23969

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

Description

As specified in the W3C Content Security Policy draft, when creating a violation report, "User agents need to ensure that the source file is the URL requested by the page, pre-redirects. If that’s not possible, user agents need to strip the URL down to an origin to avoid unintentional leakage." Under certain types of redirects, Firefox incorrectly set the source file to be the destination of the redirects. This was fixed to be the redirect destination's origin. This vulnerability affects Firefox < 86, Thunderbird < 78.8, and Firefox ESR < 78.8.

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-2021-23969

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2021-23969.html

OS impact

OSVersionStatusFixed in
arch archfixed78.8.0-1
suse slesaffected
debian debiansidfixed86.0-1
debian debianbookwormfixed78.8.0esr-1
debian debianbullseyefixed78.8.0esr-1
debian debianforkyfixed78.8.0esr-1
debian debiantrixiefixed78.8.0esr-1

References

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