Undefined Behavior in WebRTC Signaling for Firefox Browser
CVE-2026-4705

9.8CRITICAL

Key Information:

Vendor

Mozilla
Status
Firefox
Firefox Esr
Thunderbird
Vendor
CVE Published:
24 March 2026

What is CVE-2026-4705?

The vulnerability arises from undefined behavior in the WebRTC signaling component, impacting specific versions of the Firefox web browser. Users with Firefox versions below 149 and Firefox ESR versions below 140.9 are affected. This can lead to various security concerns that might compromise user privacy and browser integrity.

Affected Version(s)

Firefox < 149

Firefox ESR < 140.9

Thunderbird < 149

References

https://bugzilla.mozilla.org/show_bug.cgi?id=2014873
https://www.mozilla.org/security/advisories/mfsa2026-20/
https://www.mozilla.org/security/advisories/mfsa2026-22/

CVSS V3.1

Score:
9.8
Severity:
CRITICAL
Confidentiality:
High
Integrity:
High
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Evyatar Ben Asher, Keane Lucas, Nicholas Carlini, Newton Cheng, Daniel Freeman, Alex Gaynor, and Joel Weinberger using Claude from Anthropic
.