# CVE-2026-118027: Mozilla Firefox ESR use-after-free in Layout component

Source: https://junglewise.ai/threats/cve-2026-118027-frame-poisoning-in-the-layout-component-this-vulnerability-was  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-27. Updated: 2026-10-27  
License: CC BY 4.0 with a link back

CVE-2026-118027 · Severity: info · Published 2026-10-27

Mozilla Firefox ESR, a widely-used web browser, contains a use-after-free memory safety vulnerability in its Layout component that could allow an attacker to execute arbitrary code. An exploit of this flaw could lead to unauthorized access to user data, installation of malware, or complete compromise of the affected system.

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

## Quick answers

**Is CVE-2026-118027 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-118027 being exploited in the wild.

**How severe is CVE-2026-118027?** Informational severity, published 27 October 2026.

**Which products and versions are affected?** Mozilla Firefox ESR before 115.44.

**Is there a fix for CVE-2026-118027?** Yes: fixed in Firefox ESR 115.44. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-118027 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-118027?** Check whether you run 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 ESR 115.44

## Technical details

A use-after-free vulnerability exists in Firefox ESR's Layout component (CVE-2026-117882), allowing an attacker to execute arbitrary code through memory corruption. The vulnerability requires network access and user interaction (visiting a malicious website). This is a memory safety issue that permits code execution with the privileges of the browser process.

## Affected products

- Mozilla Firefox ESR before 115.44

## Timeline

- 2026-10-27: disclosed

## References

- [https://bugzilla.mozilla.org/show_bug.cgi?id=2045606](https://bugzilla.mozilla.org/show_bug.cgi?id=2045606)
- [https://www.mozilla.org/security/advisories/mfsa2026-119/](https://www.mozilla.org/security/advisories/mfsa2026-119/)

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- [Mozilla Firefox information disclosure in Security: RLBox](https://junglewise.ai/threats/cve-2026-124941-information-disclosure-in-the-security-rlbox-component-this)