CVE-2026-8390: Use-after-free in the JavaScript: WebAssembly component

Q: How do I fix CVE-2026-8390?

firefox: upgrade to 150.0.3. Exact commands for each OS are on this page.

Q: Is CVE-2026-8390 being exploited?

CVE-2026-8390 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-2026-8390 affect?

CVE-2026-8390 affects firefox. Severity is high (CVSS 7.3). Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 150.0.3.

Q: How urgent is CVE-2026-8390?

Priority 41/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.3REMOTEUPGRADE

CVE-2026-8390 is a high-severity flaw (CVSS 7.3) affecting firefox. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 150.0.3.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.3 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 58%)
CISA exploited list	No
Weakness	CWE-416, CWE-825
Published	2026-05-12
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

2026-05-12 14:17 UTCPublished CVE record published
2026-10-26 18:10 UTCUpdated Record last modified

mozilla firefox UPGRADE

Affected: < 150.0.3

Fixed in: 150.0.3

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 150.0.3 (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.

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-2026-8390?

firefox: upgrade to 150.0.3. Exact commands for each OS are on this page.

Is CVE-2026-8390 being exploited?

CVE-2026-8390 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-2026-8390 affect?

CVE-2026-8390 affects firefox. Severity is high (CVSS 7.3). Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 150.0.3.

How urgent is CVE-2026-8390?

Priority 41/100. High severity; Remotely exploitable, no login, no user action

Software pages

Mozilla Firefox vulnerabilities

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References

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