Description

Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

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References

Other References

https://bugzilla.mozilla.org/show_bug.cgi?id=2056164 https://www.mozilla.org/security/advisories/mfsa2026-82/ https://www.mozilla.org/security/advisories/mfsa2026-86/

Frequently Asked Questions

What is CVE-2026-84138? +

Denial-of-service in the PDF Viewer component. This vulnerability was fixed in Firefox 155 and Thunderbird 155.

How do I check if I'm vulnerable to CVE-2026-84138? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.