CVE-2019-9803

HIGH

Firefox < 66.0 - Origin Validation Error via Upgrade-Insecure-Requests Bypass

Title source: llm
STIX 2.1

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.

References (4)

Core 4
Core References
Issue Tracking, Permissions Required, Vendor Advisory x_refsource_misc
https://bugzilla.mozilla.org/show_bug.cgi?id=1515863
Issue Tracking, Vendor Advisory x_refsource_misc
https://bugzilla.mozilla.org/show_bug.cgi?id=1437009
Third Party Advisory x_refsource_misc
https://w3c.github.io/webappsec-upgrade-insecure-requests/

Scores

CVSS v3 7.4
EPSS 0.0012
EPSS Percentile 30.8%
Attack Vector NETWORK
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Details

CWE
CWE-346
Status published
Products (1)
mozilla/firefox < 66.0
Published Apr 26, 2019
Tracked Since Feb 18, 2026