VulnerabilityPublished 27 Oct 2026

CVE-2026-117890: Mozilla Firefox · JIT miscompilation in the JavaScript Engine: JIT component

Affects Mozilla FirefoxSource CVE Database V5

Not known to be exploited.

Data as of 27 Oct 2026, 15:43 UTC

Severity

High

Rated High by Threat Radar's AI analysis · CVSS not yet scored by NVD

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

AI-suggested

Users and administrators should update affected Firefox installations to version 159 or later, or Firefox ESR 153.6 or later, where the vulnerability has been fixed. Applying this official fix fully mitigates the issue.

Description

CVE-2026-117890 is a vulnerability involving just-in-time (JIT) miscompilation in the JavaScript engine component of Mozilla Firefox. This flaw was addressed and fixed in Firefox version 159 and Firefox ESR 153.6. The vulnerability is rated with high impact by Mozilla, indicating significant security concerns if exploited. There are no known exploits in the wild at this time.

Impact

The vulnerability has a high impact rating, suggesting it could allow attackers to cause significant security breaches such as code execution errors or other unintended behaviors due to JIT miscompilation. However, no active exploitation in the wild has been reported, reducing immediate risk.

Summary

This vulnerability is a JIT miscompilation issue within the JavaScript engine's JIT component in Mozilla Firefox. Such miscompilation can lead to incorrect code execution, potentially causing security issues. Mozilla fixed this vulnerability in Firefox 159 and Firefox ESR 153.6 as part of their security updates announced on October 27, 2026. The advisory classifies the impact as high, but no active exploitation has been reported.

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 27 Oct 2026, 15:43 UTC

Technical details

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