Raw vector
CVSS:3.1/AV:A/AC:H/PR:H/UI:R/S:U/C:H/I:H/A:LSummary
CVE-2026-33424 is a medium-severity Incorrect Authorization (CWE-863) vulnerability in Discourse Discourse. Its CVSS base score is 5.9 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 12th 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-4 (Information Flow Enforcement) — see the control section below for these in your framework.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-13904
Vulnerability Data
Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, an attacker can grant access to a private message topic through invites even after they lose access to that PM. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a…
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patch. No known workarounds are available.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
CWE-863 authz bypass in public-facing Discourse web app directly enables exploitation via T1190 to perform unauthorized invite actions on PM topics.
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
Mitigating Controls (NIST 800-53 r5) AI
Directly enforces authorization checks on invite operations so that a user who has already lost access to a PM cannot grant that access to others.
Enforces information-flow rules on how access rights may be propagated via invites, blocking the unauthorized flow after the inviter's own rights have been revoked.
Restricts the invite permission to the minimum set of users who currently hold legitimate access, reducing the window for the described post-revocation abuse.
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.
Defining, enforcing, and reviewing access authorizations and least privilege directly prevents incorrect 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 consistency between access rights and classification plus formal approval steps ensures that the authorization logic correctly distinguishes between entities that should and should not be granted access.
Enforcing policy-driven approval and role-change reviews stops incorrect or stale authorization decisions from remaining in effect after job changes or terminations.
By tying access rights to identity, device, location and classification, the control reduces the likelihood that an authorization decision will be based on an incorrect or bypassed policy.