CVE-2020-12409

high

Published — · Modified —

CVSS v3

—

CVSS v2

—

VIR risk

8.0

Description

When using certain blank characters in a URL, they where incorrectly rendered as spaces instead of an encoded URL. This vulnerability affects Firefox < 77.

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-2020-12409

vendor Authored 2026-05-27

Vendor advisory: suse — https://www.suse.com/security/cve/CVE-2020-12409.html

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-202006-1

OS impact

OS	Version	Status	Fixed in
arch		fixed	`77.0-1`
sles		affected
debian	sid	fixed	`77.0-1`

References

https://security.archlinux.org/ASA-202006-1
https://www.suse.com/security/cve/CVE-2020-12409.html
https://security-tracker.debian.org/tracker/CVE-2020-12409

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