CVE-2026-2804
Published: 24 February 2026
Summary
CVE-2026-2804 is a medium-severity Use After Free (CWE-416) vulnerability in Mozilla Firefox. Its CVSS base score is 5.4 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Drive-by Compromise (T1189); ranked at the 20.6th 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-16 (Memory Protection) and SI-2 (Flaw Remediation).
Deeper analysis
CVE-2026-2804 is a use-after-free vulnerability (CWE-416) in the JavaScript WebAssembly component of Mozilla Firefox and Thunderbird. It affects versions prior to Firefox 148 and Thunderbird 148, where the issue was addressed. The vulnerability carries a CVSS v3.1 base score of 5.4 (AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N), indicating medium severity with network accessibility, low attack complexity, no required privileges, but dependence on user interaction.
Remote attackers can exploit this vulnerability by tricking users into visiting a malicious website or interacting with crafted content that triggers the use-after-free in WebAssembly processing. Successful exploitation allows limited impacts, including partial disclosure of sensitive information from the browser's context and modification of some data, without affecting availability or requiring elevated privileges.
Mozilla's security advisories (MFSA 2026-13 and MFSA 2026-16) and the associated Bugzilla entry (bug 2013584) confirm the fix in Firefox 148 and Thunderbird 148. Security practitioners should prioritize updating affected browsers to these versions to mitigate the risk, as no workarounds are specified in the provided references.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8457
Vulnerability details
Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox 148 and Thunderbird 148.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Use-after-free in browser WebAssembly is directly triggered by visiting a malicious website, enabling drive-by compromise (T1189).
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires timely application of patches to remediate the use-after-free flaw, which Mozilla fixed in Firefox/Thunderbird 148.
Enforces memory protection mechanisms that can block or contain use-after-free exploitation in WebAssembly processing.
Restricts or monitors execution of mobile code such as WebAssembly delivered via web content, limiting the attack vector that requires user interaction.
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