CVE-2026-53900: Vulnerability in Mozilla Firefox for iOS
CVE-2026-53900 is a medium severity vulnerability in Mozilla Firefox for iOS where cookies set on an initial PDF request are preserved across cross-origin HTTP redirects in TemporaryDocument. This behavior allows a malicious site to inject arbitrary cookies into requests to unrelated target domains. The issue was fixed in Firefox for iOS version 152.0.
AI Analysis
Technical Summary
Firefox for iOS preserved cookies set on the initial PDF request across cross-origin HTTP redirects within TemporaryDocument. This flaw enabled a malicious site to inject arbitrary cookies into requests sent to unrelated target domains, violating cookie isolation principles. The vulnerability was reported by Muneaki Nishimura and fixed in Firefox for iOS 152.0. The CVSS v3.1 base score is 4.3 (medium severity), reflecting low complexity and no privileges required but requiring user interaction. The vendor advisory (MFSA 2026-56) confirms the fix and provides references to the underlying bug (2043204).
Potential Impact
An attacker controlling a malicious site can inject arbitrary cookies into requests to unrelated domains via cross-origin HTTP redirects when opening PDF links in Firefox for iOS. This can lead to cookie manipulation attacks, potentially affecting session integrity or user tracking. However, the impact is limited to cookie injection without direct integrity or availability compromise. No known exploits are reported in the wild.
Mitigation Recommendations
This vulnerability is fixed in Firefox for iOS version 152.0. Users and administrators should update to Firefox for iOS 152.0 or later to remediate this issue. No additional mitigation steps are required as the vendor advisory confirms the availability of an official fix.
CVE-2026-53900: Vulnerability in Mozilla Firefox for iOS
Description
CVE-2026-53900 is a medium severity vulnerability in Mozilla Firefox for iOS where cookies set on an initial PDF request are preserved across cross-origin HTTP redirects in TemporaryDocument. This behavior allows a malicious site to inject arbitrary cookies into requests to unrelated target domains. The issue was fixed in Firefox for iOS version 152.0.
CVSS v3.1
Score 4.3medium
Affected software
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Firefox for iOS preserved cookies set on the initial PDF request across cross-origin HTTP redirects within TemporaryDocument. This flaw enabled a malicious site to inject arbitrary cookies into requests sent to unrelated target domains, violating cookie isolation principles. The vulnerability was reported by Muneaki Nishimura and fixed in Firefox for iOS 152.0. The CVSS v3.1 base score is 4.3 (medium severity), reflecting low complexity and no privileges required but requiring user interaction. The vendor advisory (MFSA 2026-56) confirms the fix and provides references to the underlying bug (2043204).
Potential Impact
An attacker controlling a malicious site can inject arbitrary cookies into requests to unrelated domains via cross-origin HTTP redirects when opening PDF links in Firefox for iOS. This can lead to cookie manipulation attacks, potentially affecting session integrity or user tracking. However, the impact is limited to cookie injection without direct integrity or availability compromise. No known exploits are reported in the wild.
Mitigation Recommendations
This vulnerability is fixed in Firefox for iOS version 152.0. Users and administrators should update to Firefox for iOS 152.0 or later to remediate this issue. No additional mitigation steps are required as the vendor advisory confirms the availability of an official fix.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-06-11T06:20:46.258Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://www.mozilla.org/security/advisories/mfsa2026-56/","vendor":"Mozilla"}]
Threat ID: 6a314c870b89be6888b4cf5a
Added to database: 06/16/2026, 13:15:51 UTC
Last enriched: 06/23/2026, 15:34:47 UTC
Last updated: 08/01/2026, 07:18:01 UTC
Views: 50
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