CVE-2026-2797
Published: 24 February 2026
Summary
CVE-2026-2797 is a critical-severity Use After Free (CWE-416) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Drive-by Compromise (T1189); ranked at the 23.3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified are NIST 800-53 SI-2 (Flaw Remediation) and SC-39 (Process Isolation).
Deeper analysis
CVE-2026-2797 is a use-after-free vulnerability (CWE-416) in the JavaScript Garbage Collector (GC) component, affecting Mozilla Firefox and Thunderbird versions prior to 148. Published on 2026-02-24, it carries a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating critical severity due to its potential for severe impact without requiring user interaction or privileges.
Remote, unauthenticated attackers can exploit this vulnerability over the network with low complexity by triggering the use-after-free condition in the JavaScript GC during web content processing. Successful exploitation could allow arbitrary code execution, leading to high impacts on confidentiality, integrity, and availability, such as full browser compromise and potential sandbox escape.
Mozilla's security advisories (MFSA 2026-13 and MFSA 2026-16) confirm the issue was addressed in Firefox 148 and Thunderbird 148. Security practitioners should ensure users update to these versions or later, with further technical details available in Bugzilla entry 2013561.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8451
Vulnerability details
Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 148 and Thunderbird 148.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
UAF in browser JS GC enables remote arbitrary code execution on client via malicious web content (no auth/UI needed per CVSS), directly facilitating drive-by compromise (T1189) and exploitation for client execution (T1203).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly addresses the CVE by requiring timely flaw remediation through patching Firefox and Thunderbird to version 148 or later, eliminating the use-after-free vulnerability in the JavaScript GC.
Provides memory protections like ASLR, DEP, and stack canaries that mitigate exploitation of the use-after-free condition in the JavaScript Garbage Collector.
Enforces process isolation via browser sandboxing to limit the impact of arbitrary code execution from the JavaScript GC use-after-free, preventing full system compromise.
Hardening callouts derived
Configuration rules from DISA STIG baselines that reduce the attack surface for weaknesses of the type cited by this CVE. Derived transitively via CVE→CWE→STIG over `controls_xwalks` (authoritative rows only).
Oracle Linux 8 (1 rule)
- V-248592 OL 8 must clear memory when it is freed to prevent use-after-free attacks. via CWE-416
RHEL 8 (1 rule)
- V-230279 RHEL 8 must clear memory when it is freed to prevent use-after-free attacks. via CWE-416
RHEL 9 (1 rule)
- V-257794 RHEL 9 must clear memory when it is freed to prevent use-after-free attacks. via CWE-416