Firefox ESR, Firefox: contain code execution

Published · Updated · Digital strategy · 4 min read · By Cyber Intelligence Embassy

At a glance

Firefox ESR, Firefox: remote code execution. This 2026-07-22 case examines 3 version entries and 66 CVEs, documented releases and checks suited to browsers, using CERTFR-2026-AVI-0910.

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In this article

Retrospective for 2026-07-22, compiled on 27 October 2026. The date identifies the day being analysed; source publication and revision dates are recorded below.

What this advisory changes in your environment

The starting point is CERTFR-2026-AVI-0910, published on 2026-07-22. Its scope includes Firefox ESR, Firefox. Reported consequences are denial of service, remote code execution, impact requiring vendor clarification, security control bypass, loss of confidentiality, privilege escalation. These statements apply to the advisory’s scope; they do not assign every consequence to every product or CVE.

This case contains 3 version entries; CVE identifier count: 66. Track remediation by component: a successful overall update does not demonstrate that Firefox ESR and Firefox each received their respective fix.

Products and versions to examine

Reference
CERTFR-2026-AVI-0910
Source first published
2026-07-22
Latest source revision available for this day
2026-07-22
Named components
Firefox ESR, Firefox
CVE identifiers
CVE-2026-16354, CVE-2026-16359, CVE-2026-15719, CVE-2026-16409, CVE-2026-16404, CVE-2026-16373, CVE-2026-16386, CVE-2026-16377, CVE-2026-16357, CVE-2026-16387, CVE-2026-16352, CVE-2026-16406, CVE-2026-16363, CVE-2026-16383, CVE-2026-16393, CVE-2026-16401, CVE-2026-16378, CVE-2026-16350, CVE-2026-16369, CVE-2026-16388, CVE-2026-16402, CVE-2026-16370, CVE-2026-16362, CVE-2026-16405 … (+42)
ComponentPublished condition
Firefox ESR< 115.38
Firefox< 153
Firefox ESR< 140.13

For Firefox ESR, the published condition is “< 115.38”. Compare the version actually loaded with that condition within its own release branch. A fix installed on another edition of Firefox ESR, Firefox does not close this case.

Mechanism and prerequisites

Code execution can give an attacker the permissions of the affected process. Check the service account and reachable network destinations. Component isolation can reduce lateral movement opportunities, but does not replace the fix.

The primary record CVE-2026-16354, published by mozilla, covers Firefox, Thunderbird. The retained revision is dated 2026-07-22. Its scope is presented separately from the integrations and product groupings in CERTFR-2026-AVI-0910.

Choose the appropriate intervention

  1. Locate Firefox ESR instances, running releases and service owners. Record condition < 115.38 in the ticket alongside reference CERTFR-2026-AVI-0910.
  2. Compare the installed branch with the vendor’s Firefox ESR release notes. Prepare the package for that branch and a dependent-service test, retaining the pre-change state.
  3. After changing Firefox ESR, capture the loaded version again and verify the workflow below. Any exception needs an owner, an exposure-reduction measure and an expiry date.

Verify the fix in a real workflow

Validation scenario to adapt for Firefox ESR, Firefox: Close every Firefox ESR process, restart the browser and capture its actual version. With a test profile, exercise an internal application and check approved extensions; verify any long-term maintenance branches separately. This is a proposed defensive check, not a claim that testing was performed against third-party systems.

Limit of case CERTFR-2026-AVI-0910: this analysis replaces neither vendor prerequisites nor investigation of your logs. Only documented versions are reproduced; no attack date or victim is invented.

Questions specific to this case

Which condition should be checked for Firefox ESR?

Advisory CERTFR-2026-AVI-0910 states: Firefox ESR — < 115.38. Check the edition and running release; do not extend the published boundary to branches absent from the advisory.

Why not use one fix for Firefox ESR and Firefox?

CERTFR-2026-AVI-0910 distinguishes these components within a scope containing 3 entries. Match each branch to its own update documentation and functional check.

What is still needed to assess Firefox ESR, Firefox exposure?

For Firefox ESR, Firefox, establish the running version, the path to the component and process permissions. The sources retained for CERTFR-2026-AVI-0910 do not establish every prerequisite or active exploitation.

Sources and related reading

Practical guide : Review browser extensions before enterprise deployment

Explore the decision addressed in this case

Complete source advisory inventory

The article table may be an extract. These lists contain every affected-system entry and CVE in the specified advisory revision. They are not an inventory of your assets and do not map every CVE to every product.

Official source · CERTFR-2026-AVI-0910
Advisory revision : · Checked on :

Affected systems · 3

Original French wording is retained to avoid ambiguous translations of version conditions.

  1. Firefox ESR versions antérieures à 115.38
  2. Firefox versions antérieures à 153
  3. Firefox ESR versions antérieures à 140.13
CVE identifiers · 66