EUVD-2026-36586Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Network-accessible web API requires only a valid forum account (PR:L); integrity limited to whisper channel injection with no availability or significant confidentiality impact.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
Lifecycle Timeline
2DescriptionCVE.org
Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.4, 2026.3.0-latest to before 2026.3.1, and 2026.4.0-latest to before 2026.4.1, a flaw in how replies to whisper posts are handled allows authenticated users outside the groups configured in whispers_allowed_groups to post into a topic's staff-only whisper channel. The injected content is visible to whisperers (typically staff) alongside legitimate whispers. Only sites that have whispers enabled are affected. This issue has been patched in versions 2026.1.4, 2026.3.1, 2026.4.1, and 2026.5.0-latest.1.
AnalysisAI
Whisper channel access control in Discourse can be bypassed by any authenticated forum user, allowing injection of content into staff-only whisper threads visible to moderators and staff. Affected release trains span 2026.1.0-latest through pre-2026.1.4, 2026.3.0-latest through pre-2026.3.1, and 2026.4.0-latest through pre-2026.4.1, with all fixes confirmed by the vendor in the GitHub Security Advisory. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires an authenticated session as any registered Discourse user - the CVSS vector PR:L confirms authentication is a hard prerequisite; unauthenticated visitors cannot exploit this flaw. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N produces a Medium score of 5.4, accurately reflecting low-complexity network exploitation by authenticated users with no scope change. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An authenticated Discourse forum member without staff privileges identifies a topic containing a whisper post - detectable because a reply exists but its content is hidden. The attacker crafts an API request to post a reply explicitly targeting the whisper post's ID, triggering the flawed reply handler that fails to re-check whispers_allowed_groups membership. … |
| Remediation | Upgrade to Discourse 2026.1.4, 2026.3.1, 2026.4.1, or 2026.5.0-latest.1 as confirmed in the vendor advisory at https://github.com/discourse/discourse/security/advisories/GHSA-98ch-mgfj-wqpw. … Detailed patch versions, workarounds, and compensating controls in full report. |
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