CVE-2026-6784: Memory safety bugs present in Firefox 149 and Thunderbird 149

Q: How do I fix CVE-2026-6784?

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

Q: Is CVE-2026-6784 being exploited?

CVE-2026-6784 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-2026-6784 affect?

CVE-2026-6784 affects firefox, thunderbird. Severity is high (CVSS 7.5). Memory safety bugs present in Firefox 149 and Thunderbird 149. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability

Routine

HIGH 7.5UPGRADEUPGRADE

CVE-2026-6784 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.

Memory safety bugs present in Firefox 149 and Thunderbird 149. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox 150 and Thunderbird 150.

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.4% (top 70%)
CISA exploited list	No
Weakness	CWE-125, CWE-416, CWE-787
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 21:10 UTCUpdated Record last modified

mozilla firefox UPGRADE

Affected: < 150.0

Fixed in: 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 150.0 (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: < 150.0

Fixed in: 150.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 150.0 (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-2026-6784?

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

Is CVE-2026-6784 being exploited?

CVE-2026-6784 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-2026-6784 affect?

CVE-2026-6784 affects firefox, thunderbird. Severity is high (CVSS 7.5). Memory safety bugs present in Firefox 149 and Thunderbird 149. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability

How urgent is CVE-2026-6784?

Priority 34/100. High severity

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-2026-6747 HIGH 7.5 UPGRADE UPGRADE Use-after-free in the WebRTC component
CVE-2026-8093 HIGH 8.1 UPGRADE UPGRADE Memory safety bugs present in Thunderbird 150.0.1

References

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