CVE-2026-4718
published 2026-03-24CVE-2026-4718: Undefined behavior in the WebRTC: Signaling component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
PriorityP342high8.1CVSS 3.1
AVNACLPRNUIRSUCHIHAN
EPSS
0.30%
21.7th percentile
Undefined behavior in the WebRTC: Signaling component. This vulnerability was fixed in Firefox 149, Firefox ESR 140.9, Thunderbird 149, and Thunderbird 140.9.
Affected
12 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| debian | firefox | < firefox 149.0-1 (sid) | firefox 149.0-1 (sid) |
| debian | firefox-esr | < firefox 149.0-1 (sid) | firefox 149.0-1 (sid) |
| debian | thunderbird | < firefox 149.0-1 (sid) | firefox 149.0-1 (sid) |
| mozilla | firefox | < 140.9.0 | 140.9.0 |
| mozilla | firefox | < 149.0 | 149.0 |
| mozilla | firefox | — | — |
| mozilla | thunderbird | < 140.9.0 | 140.9.0 |
| mozilla | thunderbird | < 149.0 | 149.0 |
| mozilla | thunderbird | >= 0 < 1:140.9.0esr-1~deb11u1 | 1:140.9.0esr-1~deb11u1 |
| mozilla | thunderbird | >= 0 < 1:140.9.0esr-1~deb12u1 | 1:140.9.0esr-1~deb12u1 |
| mozilla | thunderbird | >= 0 < 1:140.9.0esr-1~deb13u1 | 1:140.9.0esr-1~deb13u1 |
| mozilla | thunderbird | >= 0 < 1:140.9.0esr-1 | 1:140.9.0esr-1 |
CVSS provenance
nvdv3.18.1HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
osv8.1HIGH
vendor_debian8.1HIGH
vendor_redhat8.1HIGH
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Red Hat
firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component
vendor_redhat·2026-03-24·CVSS 8.1
CVE-2026-4718 [HIGH] CWE-475 firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component
firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component
Undefined behavior in the WebRTC: Signaling component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
A flaw was found in Firefox and Thunderbird. The Mozilla Foundation's Security Advisory describes the following issue:
Undefined behavior in the WebRTC: Signaling component
Statement: Red Hat Product Security rates the severity of this flaw as determined by the Mozilla Foundation Security Advisory.
Package: rhel10/firefox-flatpak (Red Hat Enterprise Linux 10) - Affected
Package: rhel10/thunderbird-flatpak (Red Hat Enterprise Linux 10) - Affected
Package: firefox (Red Hat Enterprise Linux 6) - Out of support scope
Package: thunderbird (Red Hat Enterp
Debian
CVE-2026-4718: firefox - Undefined behavior in the WebRTC: Signaling component. This vulnerability affect...
vendor_debian·2026·CVSS 8.1
CVE-2026-4718 [HIGH] CVE-2026-4718: firefox - Undefined behavior in the WebRTC: Signaling component. This vulnerability affect...
Undefined behavior in the WebRTC: Signaling component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Scope: local
sid: resolved (fixed in 149.0-1)
Mozilla
Mozilla Foundation Security Advisory 2026-20: CVE-2026-4718
vendor_mozilla·CVSS 8.1
CVE-2026-4718 [HIGH] Mozilla Foundation Security Advisory 2026-20: CVE-2026-4718
Mozilla Foundation Security Advisory 2026-20
CVE: CVE-2026-4718
Product: Firefox
Impact: high
Fixed in: Firefox 149
Mozilla
Mozilla Foundation Security Advisory 2026-24: CVE-2026-4718
vendor_mozilla·CVSS 8.1
CVE-2026-4718 [HIGH] Mozilla Foundation Security Advisory 2026-24: CVE-2026-4718
Mozilla Foundation Security Advisory 2026-24
CVE: CVE-2026-4718
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 140.9
Mozilla
Mozilla Foundation Security Advisory 2026-22: CVE-2026-4718
vendor_mozilla·CVSS 8.1
CVE-2026-4718 [HIGH] Mozilla Foundation Security Advisory 2026-22: CVE-2026-4718
Mozilla Foundation Security Advisory 2026-22
CVE: CVE-2026-4718
Product: Firefox ESR
Impact: high
Fixed in: Firefox ESR 140.9
Mozilla
Mozilla Foundation Security Advisory 2026-23: CVE-2026-4718
vendor_mozilla·CVSS 8.1
CVE-2026-4718 [HIGH] Mozilla Foundation Security Advisory 2026-23: CVE-2026-4718
Mozilla Foundation Security Advisory 2026-23
CVE: CVE-2026-4718
Product: Thunderbird
Impact: high
Fixed in: Thunderbird 149
GHSA
GHSA-9r85-xf24-6724: Undefined behavior in the WebRTC: Signaling component
ghsa_unreviewed·2026-03-24
CVE-2026-4718 [HIGH] CWE-758 GHSA-9r85-xf24-6724: Undefined behavior in the WebRTC: Signaling component
Undefined behavior in the WebRTC: Signaling component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.
OSV
CVE-2026-4718: Undefined behavior in the WebRTC: Signaling component
osv·2026-03-24·CVSS 8.1
CVE-2026-4718 [HIGH] CVE-2026-4718: Undefined behavior in the WebRTC: Signaling component
Undefined behavior in the WebRTC: Signaling component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
No detection rules found.
No public exploits indexed.
Wiz
CVE-2026-4718 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.5
CVE-2026-4718 [HIGH] CVE-2026-4718 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-4718 :
NixOS vulnerability analysis and mitigation
Undefined behavior in the WebRTC: Signaling component. This vulnerability affects Firefox < 149, Firefox ESR < 140.9, Thunderbird < 149, and Thunderbird < 140.9.
Source : NVD
## 8.1
Score
Published March 24, 2026
Severity HIGH
CNA Score 8.1
Affected Technologies
NixOS
Mozilla Firefox
Has Public Exploit No
Has CISA KEV Exploit No
CISA KEV Release Date N/A
CISA KEV Due Date N/A
Exploitation Probability Percentile (EPSS) 1.7
Exploitation Probability (EPSS) N/A
Affected packages and libraries
MozillaFirefox-devel
firefox-esr
Sources
AlmaLinux 8 Severity HIGH Has Fix Added at: Mar 31, 2026
AlmaLinux 9 Severity HIGH Has Fix Added at: Mar 31, 2026
Chainguard Has Fix Added at: Mar 29, 2026
Debian 11, 12, 13,
Bugzilla
CVE-2026-4718 firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component
bugzilla·2026-03-24·CVSS 8.1
CVE-2026-4718 [HIGH] CVE-2026-4718 firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component
CVE-2026-4718 firefox: thunderbird: Undefined behavior in the WebRTC: Signaling component
Undefined behavior in the WebRTC: Signaling component. This vulnerability affects Firefox < 149 and Firefox ESR < 140.9.
Discussion:
This issue has been addressed in the following products:
Red Hat Enterprise Linux 10
Via RHSA-2026:5931 https://access.redhat.com/errata/RHSA-2026:5931
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 9
Via RHSA-2026:5930 https://access.redhat.com/errata/RHSA-2026:5930
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 8
Via RHSA-2026:5932 https://access.redhat.com/errata/RHSA-2026:5932
---
This issue has been addressed in the following products:
Red Hat Enterprise Linux 9
Via RHSA-2
2026-03-24
Published