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Discourse CVE-2026-72724

| EUVDEUVD-2026-55663 MEDIUM
Authorization Bypass Through User-Controlled Key (CWE-639)
2026-08-10 GitHub_M
Authentication Bypass Discourse
4.3
CVSS 3.1 · Vendor: GitHub_M
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Severity by source

Vendor (GitHub_M) PRIMARY
4.3 MEDIUM
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
vuln.today AI
4.3 MEDIUM

Requires authenticated account (PR:L), network-accessible endpoint with no complexity (AV:N/AC:L), read-only thread content disclosure only (C:L/I:N/A:N), scope unchanged.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

Lifecycle Timeline

3
Patch available
Aug 10, 2026 - 17:03 EUVD
Source Code Evidence Fetched
Aug 10, 2026 - 16:34 vuln.today
Analysis Generated
Aug 10, 2026 - 16:34 vuln.today

DescriptionCVE.org

Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, plugins/chat/lib/chat/onebox_handler.rb resolves Chat::Thread by route thread_id independently of the route channel_id before checking whether the user can preview the selected chat channel. An authenticated user can pair a public channel ID with a private thread ID in a /onebox.json request and obtain private thread message content. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

AnalysisAI

Discourse's Chat plugin exposes private thread message content to authenticated users who lack access to the private channel. The onebox handler in plugins/chat/lib/chat/onebox_handler.rb resolves Chat::Thread using the route's thread_id before verifying whether the requesting user can access the associated channel_id, allowing a mismatched public-channel/private-thread pair to be submitted via /onebox.json. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

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Vulnerability AssessmentAI

Exploitation The attacker must hold a valid authenticated Discourse account (PR:L per CVSS vector). … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 3.1 score of 4.3 (AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N) accurately reflects the constrained impact: the vulnerability is network-accessible with low complexity but requires an authenticated account, limits impact to confidentiality only, and does not affect integrity or availability. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Upgrade Discourse to version 2026.1.6, 2026.5.2, 2026.6.1, or 2026.7.0 depending on the branch in use; these are the vendor-confirmed fix releases per the GitHub Security Advisory GHSA-8g98-fvfc-9w48. … Detailed patch versions, workarounds, and compensating controls in full report.
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Same weakness CWE-639 – Authorization Bypass Through User-Controlled Key

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CVE-2026-72724 vulnerability details – vuln.today
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