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CVE-2026-124870

Memory-corruption in Firefox/Thunderbird JS GC can enable remote code execution.

Major vulnerability. Browser memory-corruption bug in Firefox/Thunderbird enabling potential remote code execution; affects widely deployed client software used across organizations.

CVSS
8.8Highscored by CISA
Exploited in the wild
Not knownnot in CISA KEV as of our last sync
EPSS
0.39%chance of exploitation in the next 30 daystop 67% 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

Memory-bounds error in JS GC may allow remote code execution via crafted web content or messages.

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 (fixed in 160)
  • Firefox ESR (fixed in 153.7)
  • Mozilla Thunderbird (fixed in 160)
  • Thunderbird ESR (fixed in 153.7)

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

  1. 10 Nov 2026Published
  2. 10 Nov 2026CISA SSVC assessment: exploitation nonesame day later
  3. 10 Nov 2026CVE record last updatedsame day later
  4. 12 Nov 2026Analysed by vulneraibility.com1 day later

Common questions

Is CVE-2026-124870 being exploited?

Not confirmed. CVE-2026-124870 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 0.39% probability of exploitation in the next 30 days.

How severe is CVE-2026-124870?

CVE-2026-124870 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-2026-124870?

Yes. A fix has been recorded for CVE-2026-124870. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2026-124870 affect?

CVE-2026-124870 affects Mozilla Firefox (fixed in 160), Firefox ESR (fixed in 153.7), Mozilla Thunderbird (fixed in 160), Thunderbird ESR (fixed in 153.7). Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

What should I do about CVE-2026-124870?

Install Firefox 160 / ESR 153.7 and Thunderbird 160 / ESR 153.7 immediately.

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

References

NVDCVE.orgCVE DetailsSource

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

Other links (5)

Where the data on this page comes from

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

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