CVE-2026-8388: Incorrect boundary conditions in the JavaScript Engine: JIT component

Q: How do I fix CVE-2026-8388?

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

Q: Is CVE-2026-8388 being exploited?

CVE-2026-8388 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-2026-8388 affect?

CVE-2026-8388 affects firefox. Severity is medium (CVSS 6.5). Incorrect boundary conditions in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.

Q: How urgent is CVE-2026-8388?

Priority 32/100. Remotely exploitable, no login, no user action

Routine

MEDIUM 6.5REMOTEUPGRADE

CVE-2026-8388 is a medium-severity flaw (CVSS 6.5) affecting firefox. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Incorrect boundary conditions in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 85%)
CISA exploited list	No
Weakness	CWE-119, CWE-787
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.

Advisories and coverage

Official advisories

AlmaLinux Errata: [ALSA-2026:21381] Important: thunderbird security update 2026-05-29
AlmaLinux Errata: [ALSA-2026:21378] Important: firefox security update 2026-05-29

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-2026-8388?

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

Is CVE-2026-8388 being exploited?

CVE-2026-8388 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-2026-8388 affect?

CVE-2026-8388 affects firefox. Severity is medium (CVSS 6.5). Incorrect boundary conditions in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.

How urgent is CVE-2026-8388?

Priority 32/100. Remotely exploitable, no login, no user action

Software pages

Mozilla Firefox vulnerabilities · Mozilla Thunderbird vulnerabilities

Related CVEs

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CVE-2026-7322 HIGH 7.3 UPGRADE UPGRADE Memory safety bugs present in Thunderbird ESR 140.10.0 and Thunderbird 150.0.0
CVE-2026-7324 HIGH 7.3 UPGRADE UPGRADE Memory safety bugs present in Thunderbird 150.0.0

References

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