CVE-2026-6747: Use-after-free in the WebRTC component

Q: How do I fix CVE-2026-6747?

firefox: upgrade to 140.10.0, 150.0; thunderbird: upgrade to 140.10.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-6747 being exploited?

CVE-2026-6747 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-6747 affect?

CVE-2026-6747 affects firefox, thunderbird. Severity is high (CVSS 7.5). Use-after-free in the WebRTC component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

Q: How urgent is CVE-2026-6747?

Priority 40/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADEUPGRADE

CVE-2026-6747 is a high-severity flaw (CVSS 7.5) affecting firefox, thunderbird. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Use-after-free in the WebRTC component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 66%)
CISA exploited list	No
Weakness	CWE-416, CWE-825
Published	2026-04-21
Last modified	2026-10-26

Publisher (CNA): Mozilla Corporation · Vendor: mozilla

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-21 13:16 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

mozilla firefox UPGRADE

Affected: < 140.10.0 · < 150.0

Fixed in: 140.10.0, 150.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy firefox || rpm -q firefox || firefox --version

2. UPGRADE to 140.10.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade firefox

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade firefox

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

mozilla thunderbird UPGRADE

Affected: < 140.10.0

Fixed in: 140.10.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy thunderbird || rpm -q thunderbird || thunderbird --version

2. UPGRADE to 140.10.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade thunderbird

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade thunderbird

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-6747?

firefox: upgrade to 140.10.0, 150.0; thunderbird: upgrade to 140.10.0. Exact commands for each OS are on this page.

Is CVE-2026-6747 being exploited?

CVE-2026-6747 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-6747 affect?

CVE-2026-6747 affects firefox, thunderbird. Severity is high (CVSS 7.5). Use-after-free in the WebRTC component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.

How urgent is CVE-2026-6747?

Priority 40/100. High severity; Remotely exploitable, no login, no user action

Software pages

Mozilla Firefox vulnerabilities · Mozilla Thunderbird vulnerabilities

Related CVEs

CVE-2026-6746 HIGH 7.5 UPGRADE UPGRADE Use-after-free in the DOM: Core & HTML component
CVE-2026-6758 HIGH 7.5 UPGRADE UPGRADE Use-after-free in the JavaScript: WebAssembly component
CVE-2026-6771 CRITICAL 9.8 UPGRADE UPGRADE Mitigation bypass in the DOM: Security component
CVE-2026-8093 HIGH 8.1 UPGRADE UPGRADE Memory safety bugs present in Thunderbird 150.0.1
CVE-2026-6772 HIGH 7.5 UPGRADE UPGRADE Incorrect boundary conditions in the Libraries component in NSS

References

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