Cyber Resilience

CVE-2025-68666

Access Control in Discourse ≤ 3.5.4

Published
28 January 2026
Modified
30 January 2026
Patch / advisory
CVSS Score v4 5.9
Click a component to see what it means
Raw vectorCVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS Score 0.0026 18th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2025-68666 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 18th 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-6 (Least Privilege) — see the control section below for these in your framework.

OWASP Top 10 for Web (2025)

EU & UK References

Vulnerability Data

Discourse is an open source discussion platform. In versions prior to 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0, users archives are viewable by users with moderation privileges even though moderators should not have access to the archives. Private topic/post content made by…

more

the users are leaked through the archives leading to a breach of confidentiality. This issue is patched in versions 3.5.4, 2025.11.2, 2025.12.1, and 2026.1.0. To work around this problem, a site admin can temporarily revoke the moderation role from all moderators until the Discourse instance has been upgraded to a version that has been patched.

CWE(s)

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
T1213 Data from Information Repositories Collection
Adversaries may leverage information repositories to mine valuable information.
Why these techniques?

Authorization bypass in public-facing Discourse web app directly enables exploitation for unauthorized access to private data repositories (archives/posts).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2026-33428Same product: Discourse Discourse
CVE-2026-33251Same product: Discourse Discourse
CVE-2026-27153Same product: Discourse Discourse
CVE-2026-33424Same product: Discourse Discourse
CVE-2026-27936Same product: Discourse Discourse
CVE-2025-68933Same product: Discourse Discourse
CVE-2026-24742Same product: Discourse Discourse
CVE-2026-28282Same product: Discourse Discourse
CVE-2026-28227Same product: Discourse Discourse
CVE-2025-68660Same product: Discourse Discourse

Affected Assets

discourse
discourse
2025.12.0, 2026.1.0 · ≤ 3.5.4 · 2025.11.0 — 2025.11.2

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • AC-3 Access Enforcement
  • AC-6 Least Privilege
  • AC-4 Information Flow Enforcement
Detect
Catch it (NIST detect / respond)

Harden
Shrink the surface (DISA STIG)
  • 5 hardening rules · 3 OS baselines
Validate
Prove the fix (OWASP ASVS)

Mitigating Controls (NIST 800-53 r5) AI

prevent

Directly enforces authorization rules so moderators cannot access user archives containing private posts.

prevent

Ensures moderator accounts receive only the minimum privileges required, excluding archive read rights.

prevent

Enforces information-flow policies that block private archive content from reaching moderator roles.

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.

PR.AA-05 mostly match
prevents

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.

prevents

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.

prevents

Enforcing policy-driven approval and role-change reviews stops incorrect or stale authorization decisions from remaining in effect after job changes or terminations.

prevents

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.

References