Firefox-iOS 152.0 & Before: Partial Domain Matching Cookie Leak in PDF Requests
CVE-2026-53899 Published on June 16, 2026
Cross-origin cookies could be leaked when opening a PDF link
Firefox for iOS used partial domain matching when attaching cookies to PDF requests, allowing a malicious site on a suffix domain to receive cookies belonging to the target site. This vulnerability was fixed in Firefox for iOS 152.0.
Vulnerability Analysis
CVE-2026-53899 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality and integrity, and no impact on availability.
Weakness Type
Insufficient Verification of Data Authenticity
The software does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.
Products Associated with CVE-2026-53899
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Affected Versions
Mozilla Firefox for iOS:- Version 152.0, <= * is unaffected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.