CVE-2026-100791: Vulnerability in Mozilla Firefox
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 involves a use-after-free condition within the DOM: Core & HTML component of Mozilla Firefox. Use-after-free vulnerabilities occur when a program continues to use memory after it has been freed, potentially leading to memory corruption or execution of arbitrary code. Mozilla has fixed this issue in multiple Firefox ESR and standard releases, specifically ESR 153.4, Firefox 157, ESR 115.42, and ESR 140.17. The vendor advisory classifies the impact as high and lists this vulnerability among several other memory safety issues addressed in the same security update.
Potential Impact
The vulnerability can lead to memory corruption due to use-after-free in the DOM: Core & HTML component, which may allow an attacker to execute arbitrary code or cause a denial of service. The vendor rates the impact as high. There are no known active exploits in the wild at the time of this advisory.
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 affected Firefox installations to these versions or later to remediate this issue. No additional mitigation actions are indicated by the vendor advisory.
CVE-2026-100791: Vulnerability in Mozilla Firefox
Description
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 8.8high
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 involves a use-after-free condition within the DOM: Core & HTML component of Mozilla Firefox. Use-after-free vulnerabilities occur when a program continues to use memory after it has been freed, potentially leading to memory corruption or execution of arbitrary code. Mozilla has fixed this issue in multiple Firefox ESR and standard releases, specifically ESR 153.4, Firefox 157, ESR 115.42, and ESR 140.17. The vendor advisory classifies the impact as high and lists this vulnerability among several other memory safety issues addressed in the same security update.
Potential Impact
The vulnerability can lead to memory corruption due to use-after-free in the DOM: Core & HTML component, which may allow an attacker to execute arbitrary code or cause a denial of service. The vendor rates the impact as high. There are no known active exploits in the wild at the time of this advisory.
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 affected Firefox installations to these versions or later to remediate this issue. No additional mitigation actions are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-09-26T19:17:21.137Z
- 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: 6abbb3f1f7a7c5410664098f
Added to database: 09/29/2026, 12:49:53 UTC
Last enriched: 09/29/2026, 13:18:33 UTC
Last updated: 09/29/2026, 18:20:12 UTC
Views: 3
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.