Interpretation Conflict in Firefox for iOS - CVE-2026-53900
Published: July 22, 2026
Vulnerability identifier: #VU139183
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-53900
CWE-ID: CWE-436
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Mozilla
Affected software:
Firefox for iOS
Firefox for iOS
Detailed vulnerability description
The vulnerability allows a remote attacker to inject arbitrary cookies into requests to an unrelated target domain.
The vulnerability exists due to improper cookie handling in TemporaryDocument when opening a PDF link that triggers cross-origin HTTP redirects. A remote attacker can cause cross-origin redirects from the initial PDF request to inject arbitrary cookies into requests to an unrelated target domain.
How to mitigate CVE-2026-53900
Install security update from vendor's website.