# CVE-2026-124940: Mozilla Firefox mitigation bypass in File Handling

Source: https://junglewise.ai/threats/cve-2026-124940-mitigation-bypass-in-the-file-handling-component-this  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-10. Updated: 2026-11-10  
License: CC BY 4.0 with a link back

CVE-2026-124940 · Severity: info · Published 2026-11-10

Firefox, a widely-used web browser, contains a mitigation bypass vulnerability in its file handling component that could weaken security protections for users. An attacker exploiting this flaw may be able to circumvent browser safety measures related to file operations, potentially leading to unauthorized file access or system compromise. This vulnerability affects Firefox versions prior to 160 and ESR versions before 153.7.

Technologies: [Mozilla Firefox](https://junglewise.ai/threats/technologies/firefox), [Mozilla Firefox ESR](https://junglewise.ai/threats/technologies/firefox-esr). Vendors: [Mozilla](https://junglewise.ai/threats/vendors/mozilla).

## Quick answers

**Is CVE-2026-124940 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-124940 being exploited in the wild.

**How severe is CVE-2026-124940?** Informational severity, published 10 November 2026.

**Which products and versions are affected?** Mozilla Firefox before 160; Mozilla Firefox ESR before 153.7.

**Is there a fix for CVE-2026-124940?** Yes: fixed in Firefox 160, Firefox ESR 153.7. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-124940 attacked?** It is in a web application.

**Am I affected by CVE-2026-124940?** Check whether you run Mozilla Firefox or Mozilla Firefox ESR at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in Firefox 160, Firefox ESR 153.7

## Technical details

The vulnerability is a mitigation bypass in Firefox's File Handling component, allowing an attacker to circumvent existing security protections through network or local attack vectors. The specific attack preconditions and exact impact are not detailed in available sources, but the bypass of file-handling mitigations could enable unauthorized file system access. Fixes are available in Firefox 160 and Firefox ESR 153.7.

## Affected products

- Mozilla Firefox before 160
- Mozilla Firefox ESR before 153.7

## Timeline

- 2026-11-10: disclosed

## References

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2076948](https://bugzilla.mozilla.org/show_bug.cgi?id=2076948)
- [https://www.mozilla.org/security/advisories/mfsa2026-125/](https://www.mozilla.org/security/advisories/mfsa2026-125/)

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