CVE-2026-2784
Published: 24 February 2026
Summary
CVE-2026-2784 is a critical-severity Authentication Bypass Using an Alternate Path or Channel (CWE-288) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Client Execution (T1203); ranked at the 34.6th 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-2 (Flaw Remediation) and RA-5 (Vulnerability Monitoring and Scanning).
Deeper analysis
CVE-2026-2784 is a mitigation bypass vulnerability in the DOM Security component affecting Mozilla Firefox prior to version 148, Firefox ESR prior to 140.8, Thunderbird prior to 148, and Thunderbird prior to 140.8. Assigned CWE-288 and published on 2026-02-24, it carries a CVSS v3.1 base score of 9.8, indicating critical severity due to its potential for high impact on confidentiality, integrity, and availability.
The vulnerability enables exploitation over a network by unauthenticated attackers with low complexity and no user interaction required. Successful exploitation allows attackers to bypass security mitigations in the DOM, potentially leading to arbitrary code execution or other severe compromises as reflected in the high impact metrics (C:H/I:H/A:H) and unchanged scope (S:U).
Mozilla security advisories (MFSA 2026-13, 15, 16, 17) and the associated Bugzilla entry (2012984) confirm the issue was addressed in the listed fixed versions, recommending immediate upgrades to mitigate the bypass. No additional workarounds are detailed in the provided references.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-8505
Vulnerability details
Mitigation bypass in the DOM: Security component. This vulnerability was fixed in Firefox 148, Firefox ESR 140.8, Thunderbird 148, and Thunderbird 140.8.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The CVE describes a remote mitigation bypass in a client application (Firefox/Thunderbird) enabling unauthenticated arbitrary code execution with no user interaction, which directly maps to exploitation of client software for code execution.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mandates timely identification, reporting, and correction of flaws like CVE-2026-2784 via vendor patches to prevent DOM security mitigation bypass exploitation.
Ensures receipt and implementation of security advisories such as Mozilla MFSA 2026-13, enabling prompt upgrades to mitigate this Firefox DOM vulnerability.
Vulnerability scanning detects systems running vulnerable Firefox versions prior to 148 or ESR 140.8 affected by CVE-2026-2784.
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 (2 rules)
- V-248598 There must be no ".shosts" files on the OL 8 operating system. via CWE-288
- V-248827 OL 8 must not have the rsh-server package installed. via CWE-288
Oracle Linux 9 (2 rules)
- V-271757 OL 9 file systems must not contain shosts.equiv files. via CWE-288
- V-271758 OL 9 file systems must not contain .shosts files. via CWE-288
RHEL 7 (3 rules)
- V-204424 The Red Hat Enterprise Linux operating system must not allow accounts configured with blank or null passwords. via CWE-288
- V-204440 Red Hat Enterprise Linux operating systems version 7.2 or newer using Unified Extensible Firmware Interface (UEFI) must require authentication upon booting into single-user and maintenance modes. via CWE-288
- V-204442 The Red Hat Enterprise Linux operating system must not have the rsh-server package installed. via CWE-288