# CVE-2026-124917: Mozilla Firefox use-after-free in Widget: Gtk sandbox escape

Source: https://junglewise.ai/threats/cve-2026-124917-sandbox-escape-due-to-use-after-free-in-the-widget-gtk-component  
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-2026-124917 · Severity: info · Published 2026-11-10

Firefox is a web browser used by millions worldwide to access the internet. A use-after-free memory vulnerability in the Gtk widget component allows an attacker to escape the browser's sandbox and potentially execute arbitrary code with the privileges of the user running Firefox. This could lead to complete compromise of the user's system.

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-2026-124917 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-124917 being exploited in the wild.

**How severe is CVE-2026-124917?** 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-2026-124917?** 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-2026-124917 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-124917?** 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

A use-after-free vulnerability in Firefox's Widget: Gtk component allows sandbox escape. The vulnerability is triggered when a freed memory region in the Gtk widget handling is accessed during browser operation, potentially allowing an attacker to execute arbitrary code outside the sandbox boundary with network-based attack vector requiring user interaction (opening a malicious web page).

## Affected products

- Mozilla Firefox before 160
- Mozilla Firefox ESR before 153.7

## Timeline

- 2026-11-10: disclosed
- 2026-11-10: patched

## References

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2058648](https://bugzilla.mozilla.org/show_bug.cgi?id=2058648)
- [https://www.mozilla.org/security/advisories/mfsa2026-125/](https://www.mozilla.org/security/advisories/mfsa2026-125/)

## Related threats

- [Firefox ESR use-after-free in Audio/Video component](https://junglewise.ai/threats/cve-2026-124952-use-after-free-in-the-audio-video-component-this-vulnerability)
- [Firefox privilege escalation in Nimbus Desktop Client](https://junglewise.ai/threats/cve-2026-124951-privilege-escalation-in-the-nimbus-desktop-client-component-this)
- [Firefox same-origin policy bypass in CSS Parsing and Computation](https://junglewise.ai/threats/cve-2026-124950-same-origin-policy-bypass-in-the-css-parsing-and-computation)
- [Firefox other issue in SVG component](https://junglewise.ai/threats/cve-2026-124949-other-issue-in-the-svg-component-this-vulnerability-was-fixed-in)
- [Mozilla Firefox use-after-free in Graphics component](https://junglewise.ai/threats/cve-2026-124948-incorrect-boundary-conditions-use-after-free-in-the-graphics)