CVE-2026-4718 — Reliance on Undefined, Unspecified, or Implementation-Defined Behavior in Mozilla Firefox

CWE-758 — Reliance on Undefined, Unspecified, or Implementation-Defined BehaviorCWE-475 — Undefined Behavior for Input to API12 documents9 sources
Severity
8.1HIGHNVD
EPSS
0.0%
top 98.33%
CISA KEV
Not in KEV
Exploit
No known exploits
Affected products
2
Mozilla ThunderbirdMozilla Firefox
Timeline
PublishedMar 24

Description

Undefined behavior in the WebRTC: Signaling component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:NExploitability: 2.8 | Impact: 5.2

Affected Packages3 packages

▶NVDmozilla/firefox< 140.9.0+1
▶NVDmozilla/thunderbird< 140.9.0+1
▶Debianmozilla/thunderbird< 1:140.9.0esr-1~deb11u1+3

🔴Vulnerability Details

3
GHSA
GHSA-9r85-xf24-6724: Undefined behavior in the WebRTC: Signaling component↗2026-03-24
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OSV
CVE-2026-4718: Undefined behavior in the WebRTC: Signaling component↗2026-03-24
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CVEList
Undefined behavior in the WebRTC: Signaling component↗2026-03-24
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📋Vendor Advisories

6
Red Hat
firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component↗2026-03-24
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Debian
CVE-2026-4718: firefox - Undefined behavior in the WebRTC: Signaling component. This vulnerability affect...↗2026
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Mozilla
Mozilla Foundation Security Advisory 2026-20: CVE-2026-4718↗
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Mozilla
Mozilla Foundation Security Advisory 2026-24: CVE-2026-4718↗
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Mozilla
Mozilla Foundation Security Advisory 2026-22: CVE-2026-4718↗
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🕵️Threat Intelligence

1
Wiz
CVE-2026-4718 Impact, Exploitability, and Mitigation Steps | Wiz↗
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💬Community

1
Bugzilla
CVE-2026-4718 firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component↗2026-03-24
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CVE-2026-4718 — Mozilla Firefox vulnerability | cvebase