CVE-2026-16377
A security flaw in the PDF Viewer component allows attackers to bypass existing security protections. This flaw could allow unauthorized access or control during the viewing of PDF files.
An official fix is available, so this entry is kept for 30 days and then removed automatically.
Who is affected
Users of Firefox (versions prior to 153 or ESR 140.13) and Thunderbird (versions prior to 153 or 140.13) who use the built-in PDF Viewer component.
Real-world impact
An attacker could potentially bypass security measures to gain unauthorized access to sensitive information or execute malicious actions while a user is viewing a PDF document.
Why this severity
This is a critical vulnerability because it can be exploited remotely over the network without any user interaction or special privileges, potentially leading to a total loss of confidentiality, integrity, and availability.
What to do about it
- 01Upgrade Firefox to version 153 or later.
- 02Upgrade Firefox ESR to version 140.13 or later.
- 03Upgrade Thunderbird to version 153 or later.
- 04Upgrade Thunderbird to version 140.13 or later.
NVD-referenced vendor advisory
Timeline
- Jul 21, 2026 · 12d agoPublishedDisclosed and added to the National Vulnerability Database.
- Jul 23, 2026 · 10d agoOfficial fix availableA vendor patch or mitigation now exists — see the remediation steps above.
- Jul 24, 2026 · 9d agoAdvisory updatedThe NVD record was last revised.
How it’s attacked
References & advisories
- bugzilla.mozilla.org/show_bug.cgipermissions required
- mozilla.org/security/advisories/mfsa202…vendor advisory
- mozilla.org/security/advisories/mfsa202…vendor advisory
- mozilla.org/security/advisories/mfsa202…vendor advisory
- mozilla.org/security/advisories/mfsa202…vendor advisory