Input validation error in Firefox for iOS - CVE-2026-53899
Published: July 22, 2026
Vulnerability identifier: #VU139182
CSH Severity: Medium
CVSS v4: 6.7 [CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-53899
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to disclose sensitive information.
The vulnerability exists due to improper cookie domain validation in PDF requests when opening a PDF link. A remote attacker can host a malicious site on a suffix domain to disclose sensitive information.
Affected software
Firefox for iOS
How to mitigate CVE-2026-53899
Install security update from vendor's website.
Firefox for iOS - update to 152.0