CVE-2026-100778: Vulnerability in Mozilla Firefox
Sandbox escape due to use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
AI Analysis
Technical Summary
This vulnerability is a sandbox escape due to a use-after-free condition in the DOM: Core & HTML component of Mozilla Firefox. Use-after-free vulnerabilities occur when a program continues to use a pointer after it has been freed, potentially leading to memory corruption and security breaches. This specific flaw allows an attacker to escape the browser sandbox, which is designed to isolate web content and limit the impact of malicious code. The vulnerability was addressed and fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
Potential Impact
The vulnerability enables sandbox escape, which can allow an attacker to execute code outside the browser's restricted environment, potentially leading to further compromise of the host system. The impact is rated high by the vendor.
Mitigation Recommendations
Mozilla has released official fixes for this vulnerability in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. Users and administrators should update to these versions or later to remediate the issue. No additional mitigation steps are required beyond applying the official patches.
CVE-2026-100778: Vulnerability in Mozilla Firefox
Description
Sandbox escape due to use-after-free in the DOM: Core & HTML component. This vulnerability was fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
CVSS v3.1
Score 9.6critical
Affected software
Mozilla
Firefox
pkg:github/mozilla/firefoxRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability is a sandbox escape due to a use-after-free condition in the DOM: Core & HTML component of Mozilla Firefox. Use-after-free vulnerabilities occur when a program continues to use a pointer after it has been freed, potentially leading to memory corruption and security breaches. This specific flaw allows an attacker to escape the browser sandbox, which is designed to isolate web content and limit the impact of malicious code. The vulnerability was addressed and fixed in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
Potential Impact
The vulnerability enables sandbox escape, which can allow an attacker to execute code outside the browser's restricted environment, potentially leading to further compromise of the host system. The impact is rated high by the vendor.
Mitigation Recommendations
Mozilla has released official fixes for this vulnerability in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. Users and administrators should update to these versions or later to remediate the issue. No additional mitigation steps are required beyond applying the official patches.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-09-26T19:16:48.272Z
- State
- PUBLISHED
- Vendor Advisory Urls
- [{"url":"https://www.mozilla.org/security/advisories/mfsa2026-100/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-97/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-98/","vendor":"Mozilla"},{"url":"https://www.mozilla.org/security/advisories/mfsa2026-99/","vendor":"Mozilla"}]
Threat ID: 6abbb3eff7a7c5410664097b
Added to database: 09/29/2026, 12:49:51 UTC
Last enriched: 09/29/2026, 13:32:53 UTC
Last updated: 09/29/2026, 18:20:12 UTC
Views: 4
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