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Vulnerabilities

Vulnerability · CVE-2026-109733

JIT miscompilation in the JavaScript Engine: JIT component

Published Oct 13, 2026 · catalog updated Oct 15, 2026 · Mozilla Firefox

Severity
Unknown—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.3%
Remediation
Advisory link
Affected products
vendor Mozilla Firefox · vendor Mozilla Thunderbird

JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Technical analysis

Mechanism and impact are interpreted from ingested advisories — not independent exploit research.

  • CWE classification

    No CWE identifiers stored yet.

  • Prerequisites and impact

    Follow the original vendor advisory for access prerequisites and impact. This catalog does not invent exploit conditions.

How to fix CVE-2026-109733

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2026-109733 is a unknown public vulnerability record for Mozilla Firefox. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether Mozilla Firefox is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: Mozilla Firefox; Mozilla Thunderbird. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: EPSS 0.3% (30-day exploitation probability). It is not currently listed in the CISA Known Exploited catalog. Sources contributing to this record: circl, cve_org, epss, mozilla. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Related intelligence

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 13, 2026 · CIRCL Vulnerability Lookup

    Detected

    JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

  2. Oct 15, 2026 · CIRCL Vulnerability Lookup

    Updated

    JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 158, Firefox ESR 115.43, Firefox ESR 153.5, Thunderbird 158, and Thunderbird 153.5.

Affected versions

Enter an installed version to get a verified affected / not-affected result against the ranges below.

  • vendor Mozilla Firefoxversion unspecified
  • vendor Mozilla Thunderbirdversion unspecified

Sources

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.