CVE-2026-100784: Vulnerability in Mozilla Firefox
Use-after-free in the Layout: Text and Fonts 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 in the Layout: Text and Fonts component of Mozilla Firefox. Use-after-free vulnerabilities occur when a program continues to use a pointer after the memory it points to has been freed, potentially leading to memory corruption or other unintended behavior. Mozilla has fixed this issue in multiple Firefox ESR versions (115.42, 140.17, 153.4) and Firefox 157. The vendor advisory lists this vulnerability among several high-impact memory safety issues resolved in the September 29, 2026 security update.
Potential Impact
The vulnerability is classified with high impact due to its memory safety nature, which could allow an attacker to cause a crash or potentially execute arbitrary code. However, there are no reports of active exploitation in the wild. The fix mitigates the risk by correcting the use-after-free condition.
Mitigation Recommendations
A fix is available and has been released in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. Users and administrators should update to these or later versions to remediate this vulnerability. No additional mitigation steps are indicated by the vendor advisory.
CVE-2026-100784: Vulnerability in Mozilla Firefox
Description
Use-after-free in the Layout: Text and Fonts 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 in the Layout: Text and Fonts component of Mozilla Firefox. Use-after-free vulnerabilities occur when a program continues to use a pointer after the memory it points to has been freed, potentially leading to memory corruption or other unintended behavior. Mozilla has fixed this issue in multiple Firefox ESR versions (115.42, 140.17, 153.4) and Firefox 157. The vendor advisory lists this vulnerability among several high-impact memory safety issues resolved in the September 29, 2026 security update.
Potential Impact
The vulnerability is classified with high impact due to its memory safety nature, which could allow an attacker to cause a crash or potentially execute arbitrary code. However, there are no reports of active exploitation in the wild. The fix mitigates the risk by correcting the use-after-free condition.
Mitigation Recommendations
A fix is available and has been released in Firefox ESR 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17. Users and administrators should update to these or later versions to remediate this vulnerability. No additional mitigation steps are indicated by the vendor advisory.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- mozilla
- Date Reserved
- 2026-09-26T19:17:03.000Z
- 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: 6abbb3eff7a7c54106640981
Added to database: 09/29/2026, 12:49:51 UTC
Last enriched: 09/29/2026, 13:18:58 UTC
Last updated: 09/29/2026, 18:20:12 UTC
Views: 2
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