{"cve":"CVE-2019-9803","nvd":{"published":"2019-04-26T17:29:03.257","modified":"2026-06-17T02:44:29.140","status":"Modified","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.","cvss_v4":null,"cvss_v3":{"version":"3.0","vector":"CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N","score":7.4},"cwes":["CWE-346"],"references":["https://bugzilla.mozilla.org/show_bug.cgi?id=1437009","https://bugzilla.mozilla.org/show_bug.cgi?id=1515863","https://w3c.github.io/webappsec-upgrade-insecure-requests/","https://www.mozilla.org/security/advisories/mfsa2019-07/","https://bugzilla.mozilla.org/show_bug.cgi?id=1437009"],"products":["mozilla:firefox"],"source":"nvd","synced_at":"2026-10-19T20:56:19.218283075+00:00"},"epss":{"cve":"CVE-2019-9803","score":0.00559,"percentile":0.4655,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}