Applications

CVE-2026-124943

Use-after-free in Firefox/Thunderbird layout enabling potential remote code execution.

Major vulnerability. High-severity memory-corruption (use-after-free) in widely used Mozilla browsers enabling potential remote code execution; affects many organizations and deserves broad notice.

CVSS: 8.8Highscored by CISA
Exploited in the wild: Not knownnot in CISA KEV as of our last sync
EPSS: 0.32%chance of exploitation in the next 30 daystop 75% of scored CVEsFIRST score of 11 Nov 2026
Fix: Patch availablesee the advisories in the references
Published: 10 Nov 2026analysed here 12 Nov 2026

Summary

Impact

Potential remote code execution or crash via crafted web content exploiting layout use-after-free (CWE-416).

The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.

Affected products

Products named in our analysis

Mozilla Firefox < 160
Mozilla Thunderbird < 160
Gecko-based applications

Fix and mitigation

Action required

Immediate action required

Remediation steps (AI-written)

Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.

Exploitation evidence

CISA KEV catalog: Not listed as of our last sync.
Public exploit code: None on record in Exploit-DB, Metasploit, Nuclei templates or PoC-in-GitHub.
CISA SSVC: exploitation none, automatable no, technical impact totalAssessed by CISA 10 Nov 2026 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.

Timeline

10 Nov 2026Published
10 Nov 2026CISA SSVC assessment: exploitation nonesame day later
10 Nov 2026CVE record last updatedsame day later
12 Nov 2026Analysed by vulneraibility.com1 day later

Common questions

Is CVE-2026-124943 being exploited?

Not confirmed. CVE-2026-124943 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.32% probability of exploitation in the next 30 days.

How severe is CVE-2026-124943?

CVE-2026-124943 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2026-124943?

Yes. A fix has been recorded for CVE-2026-124943. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2026-124943 affect?

CVE-2026-124943 affects Mozilla Firefox < 160, Mozilla Thunderbird < 160, Gecko-based applications. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

What should I do about CVE-2026-124943?

Upgrade to Firefox/Thunderbird 160+ immediately.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

References

NVD CVE.org CVE Details Source

3 references in the CVE record, grouped by the tags the record gives them.

Where the data on this page comes from

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
CISA Vulnrichment (ADP): SSVC decision points
FIRST EPSS: exploit probability and percentile

Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.

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