CVE-2026-84133
Mozilla Firefox ≤ 153.2.0
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-84133 is a critical-severity Origin Validation Error (CWE-346) vulnerability in Mozilla Firefox. Its CVSS base score is 9.8 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique ARP Cache Poisoning (T1557.002); ranked at the 8th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-4 (Information Flow Enforcement) and IA-3 (Device Identification and Authentication) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-69081
Vulnerability Data
Site isolation issue in the DOM: Push Subscriptions component. This vulnerability was fixed in Firefox 155, Firefox ESR 153.2, Thunderbird 155, and Thunderbird 153.2.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 3 hardening rules · 1 OS baseline
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Mitigating Controls (NIST 800-53 r5) AI
Information flow enforcement directly requires validating the source of data before allowing transmission or receipt.
Device identification and authentication mandates verifying the source before establishing connections.
Session authenticity mechanisms require validation that communications originate from the expected party.
Boundary protection at interfaces enforces checks on the origin of incoming communications.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Documenting authorized flows supports origin validation by defining expected sources.
Authentication directly verifies the source of users/services/hardware, mitigating origin validation failures.
Verifying identity assertions enforces origin validation for conveyed claims.
Protecting networks from unauthorized access requires origin checks on communication sources.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Network security controls enforce origin validation at network boundaries.
Security of network services includes validating the authenticity of service endpoints.
Network segregation reduces exposure but does not directly validate origins.
Application security requirements explicitly call for origin validation of inputs and communications.
Secure architecture principles encourage origin checks but do not mandate them.
Secure coding practices include implementing proper origin validation to prevent spoofing.
Hardening callouts derived
Configuration rules from DISA STIG baselines that bear on weaknesses of the type cited by this CVE. Each rule is shown with the relationship its mapping actually records, against the CWE it was authored against. Derived via CVE→CWE over `controls_xwalks` (higher-evidence rows only; rows rated `none` are excluded).
Oracle Linux 8 (3 rules)
- V-248574 YUM must be configured to prevent the installation of patches, service packs, device drivers, or OL 8 system components that have not been digitally signed using a certificate that is recognized and approved by the organization. prevents CWE-346
- V-248575 OL 8 must prevent the installation of software, patches, service packs, device drivers, or operating system components of local packages without verification they have been digitally signed using a certificate that is issued by a Certificate Authority (CA) that is recognized and approved by the organization. prevents CWE-346
- V-248827 OL 8 must not have the rsh-server package installed. prevents CWE-346