CVE-2019-9803 - CVE House
Back to Database
Status published High CVE-2019-9803

The Upgrade-Insecure-Requests (UIR) specification states that if UIR is enabled...

Vulnerability 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.

Impact Analysis

Refer to official advisory for detailed impact metrics.

Remediation

Ensure systems are updated to the latest vendor-supplied patch levels.

THREAT MONITOR

Am I Vulnerable?

Launch our assessment wizard to check if your infrastructure is exposed to • CVE-2019-9803

Credits & Attribution

No credits recorded in the NVD database.

References

More from Mozilla

View All →
CVE-2025-9187
Memory safety bugs fixed in Firefox 142 and Thunderbird 142
Unknown 0
CVE-2025-9186
Spoofing issue in the Address Bar component of Firefox Focus for Android
Unknown 0
CVE-2025-9185
Memory safety bugs fixed in Firefox ESR 115.27, Firefox ESR 128.14, Thunderbird ESR 128.14, Firefox ESR 140.2, Thunderbird ESR 140.2, Firefox 142 and Thunderbird 142
Unknown 0
CVE-2025-9184
Memory safety bugs fixed in Firefox ESR 140.2, Thunderbird ESR 140.2, Firefox 142 and Thunderbird 142
Unknown 0
CVE-2025-9183
Spoofing issue in the Address Bar component
Unknown 0

Affected Vendor

Affected Software

Firefox
Vulnerable Versions:
unspecified

Timeline

Official Publish: April 26th, 2019
Last Modified: August 4th, 2024
Added to House: July 20th, 2026

CVSS Vectors

V3: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

Weaknesses (CWE)

No CWE data available

MITRE ATT&CK TTPs

No associated TTPs found for this vulnerability.