CVE-2019-9803

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

Description

The Upgrade-Insecure-Requests (UIR) specification states that if UIR is enabled through Content Security Policy (CSP), navigation to a same-origin URL must be upgraded to HTTPS. Firefox will incorrectly navigate to an HTTP URL rather than perform the security upgrade requested by the CSP in some circumstances, allowing for potential man-in-the-middle attacks on the linked resources. This vulnerability affects Firefox < 66.

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-2019-9803

vendor Authored 2026-05-27

Vendor advisory: arch — https://security.archlinux.org/ASA-201903-11

OS impact

OSVersionStatusFixed in
arch archfixed66.0-1
debian debiansidfixed66.0-1

References

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