# CERT-FR Flags Firefox Vulnerability

Published: 2026-11-04 · Severity: routine
Canonical: https://vorant.io/reports/a0918d46-6ef3-561b-8309-dcc79bd14d74/cert-fr-flags-firefox-vulnerability
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> CERT-FR advisory warns of an unspecified security flaw in Mozilla Firefox versions before 159.0.1; patch available.

Source: cert.cyber.gouv.fr — https://www.cert.cyber.gouv.fr/avis/CERTFR-2026-AVI-1455

## What to check

- Applies to: The 1 CVE named below. Whether you run an affected version is not assessed: check the versions the source lists.
- Exploitation: No exploitation in the wild and no public exploit is recorded for the CVEs named.

CERT-FR issued an advisory regarding a vulnerability in Mozilla Firefox affecting versions prior to 159.0.1. The specific risk and technical details were not disclosed by Mozilla in the referenced bulletin (mfsa2026-123), though the issue is tracked as CVE-2026-120572. No information was provided on whether the vulnerability is being actively exploited in the wild.

Defenders should update affected Firefox installations to version 159.0.1 or later as soon as possible, following guidance from Mozilla's official security advisory. As the vendor has not specified the nature of the risk (e.g., RCE, memory corruption, sandbox escape), organizations should treat this as a standard browser security patch and prioritize deployment according to their patch management policies for widely used client software.

## Mentioned in this report

- Vulnerabilities: CVE-2026-120572

Source reporting: https://www.cert.cyber.gouv.fr/avis/CERTFR-2026-AVI-1455

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