CVE-2026-2770
Published: 24 February 2026
Summary
CVE-2026-2770 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 37.3th 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 RA-5 (Vulnerability Monitoring and Scanning).
Deeper analysis
CVE-2026-2770 is a use-after-free vulnerability (CWE-416) in the DOM: Bindings (WebIDL) component of Mozilla Firefox and Thunderbird. It affects versions of Firefox prior to 148, Firefox ESR prior to 115.33 and 140.8, and Thunderbird prior to 148 and 140.8. The issue was publicly disclosed on 2026-02-24 and carries a CVSS v3.1 base score of 9.8, indicating critical severity due to its potential for high-impact exploitation.
Remote attackers require no privileges or user interaction to exploit this vulnerability over the network with low attack complexity and no scope change. Successful exploitation could result in high confidentiality, integrity, and availability impacts, potentially allowing arbitrary code execution within the browser's rendering engine.
Mozilla's security advisories (MFSA 2026-13 through 2026-16) and Bugzilla entry 2014585 confirm the vulnerability was addressed in the specified fixed releases. Security practitioners should prioritize updating affected Firefox and Thunderbird installations to the patched versions to mitigate the risk.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8491
Vulnerability details
Use-after-free in the DOM: Bindings (WebIDL) component. This vulnerability was fixed in Firefox 148, Firefox ESR 115.33, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Use-after-free in browser DOM/WebIDL enables remote arbitrary code execution (no user interaction) via malicious web content, directly mapping to drive-by initial access and client-side exploitation for execution.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Requires timely remediation of identified flaws through patching, directly addressing the use-after-free vulnerability fixed in updated Firefox and Thunderbird versions.
Enables vulnerability scanning to identify systems running vulnerable Firefox or Thunderbird versions affected by this CVE.
Implements memory protection mechanisms like ASLR and DEP to mitigate exploitation of the use-after-free vulnerability in the browser's DOM bindings.
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