Raw vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:NSummary
CVE-2026-33426 is a low-severity Missing Authorization (CWE-862) vulnerability in Discourse Discourse. Its CVSS base score is 3.5 (Low).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 6th 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-3 (Access Enforcement) and AC-16 (Security and Privacy Attributes) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-13908
Vulnerability Data
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, users with tag-editing permissions could edit and create synonyms for tags hidden in restricted tag groups, even if they lacked visibility into those tags. Versions 2026.3.0-latest.1, 2026.2.1,…
more
and 2026.1.2 contain a patch. No known workarounds are available.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CWE-862 authorization bypass in public-facing web app (Discourse) directly enables exploitation of the application to access/modify restricted resources.
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
Mitigating Controls (NIST 800-53 r5) AI
Directly enforces authorization checks so that tag-edit permissions cannot be used to modify or synonymize tags the user is not authorized to see.
Ensures tag-editing rights are granted only at the granularity needed, preventing over-privileged accounts from reaching hidden restricted tags.
Binds visibility and edit attributes to tags so that permission decisions can correctly restrict operations on hidden tag-group members.
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.
Explicitly requires defining, enforcing, and reviewing authorizations and least privilege, directly preventing missing authorization checks.
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.
Requiring authentication and credentials before any access occurs eliminates the absence of authorization checks that would otherwise allow an unauthenticated actor to reach protected resources.
Requiring formal authorization of every access request before rights are granted ensures that checks for required permissions are performed, preventing missing authorization checks from being introduced.
Mandatory authorization checks and central records of granted rights ensure that every access attempt is preceded by an explicit decision rather than relying on missing checks.
Segregating the approval of access rights from their implementation provides an independent check that reduces the impact of missing authorization checks in the resulting system configuration.
By requiring competent outsiders to verify that every function enforces the need-to-know principle, the control lowers the likelihood that missing authorization checks persist undetected.
Defining authorization responsibilities and reviewing risk-treatment progress throughout the project lifecycle catches missing authorization checks before the system is deployed.