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CVE-2026-31869

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the ComposerController#mentions endpoint reveals hidden group membership to any authenticated user who can message the group. By supplying allowed_names referencing a hidden-membership group and probing arbitrary usernames, an attacker can infer membership based on whether user_reasons returns "private" for a given user. This bypasses group member-visibility controls. Versions 2026.3.0-l
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:28235dad07696b515449fffede9d629ed1a48056e1c6e69b4c59c9ee5ef5811d
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
1

Preserved source conflicts

No provider value was silently selected as the winner.

cwe · 3 assertions

{"cweId":"CWE-200","description":"CWE-200: Exposure of Sensitive Information to an Unauthorized Actor","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:663d692e7c0c4b748bf0133e213b6f7056e99886c1c780f5a13f5f7d63c47009 · sha256:4d34da0ddbbc6c87… · /containers/cna/problemTypes/0/descriptions/0

{"cweId":"CWE-639","description":"CWE-639: Authorization Bypass Through User-Controlled Key","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:663d692e7c0c4b748bf0133e213b6f7056e99886c1c780f5a13f5f7d63c47009 · sha256:4d34da0ddbbc6c87… · /containers/cna/problemTypes/2/descriptions/0

{"cweId":"CWE-285","description":"CWE-285: Improper Authorization","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:663d692e7c0c4b748bf0133e213b6f7056e99886c1c780f5a13f5f7d63c47009 · sha256:4d34da0ddbbc6c87… · /containers/cna/problemTypes/1/descriptions/0

Affected products and versions

1 source assertion
{"product":"discourse","vendor":"discourse","versions":[{"status":"affected","version":">= 2026.1.0-latest, < 2026.1.2"},{"status":"affected","version":">= 2026.2.0-latest, < 2026.2.1"},{"status":"affected","version":"= 2026.3.0-latest"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:663d692e7c0c4b748bf0133e213b6f7056e99886c1c780f5a13f5f7d63c47009 · sha256:4d34da0ddbbc6c87… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion
{"metric":{"attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":5.3,"baseSeverity":"MEDIUM","privilegesRequired":"LOW","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"NONE","vulnConfidentialityImpact":"LOW","vulnIntegrityImpact":"NONE"},"metric_type":"cvssV4_0"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:663d692e7c0c4b748bf0133e213b6f7056e99886c1c780f5a13f5f7d63c47009 · sha256:4d34da0ddbbc6c87… · /containers/cna/metrics/0/cvssV4_0

CWE assertions

3 source assertions
{"cweId":"CWE-200","description":"CWE-200: Exposure of Sensitive Information to an Unauthorized Actor","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:663d692e7c0c4b748bf0133e213b6f7056e99886c1c780f5a13f5f7d63c47009 · sha256:4d34da0ddbbc6c87… · /containers/cna/problemTypes/0/descriptions/0
{"cweId":"CWE-639","description":"CWE-639: Authorization Bypass Through User-Controlled Key","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:663d692e7c0c4b748bf0133e213b6f7056e99886c1c780f5a13f5f7d63c47009 · sha256:4d34da0ddbbc6c87… · /containers/cna/problemTypes/2/descriptions/0
{"cweId":"CWE-285","description":"CWE-285: Improper Authorization","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:663d692e7c0c4b748bf0133e213b6f7056e99886c1c780f5a13f5f7d63c47009 · sha256:4d34da0ddbbc6c87… · /containers/cna/problemTypes/1/descriptions/0

Source references

1 source assertion
{"name":"https://github.com/discourse/discourse/security/advisories/GHSA-5f9h-vp7v-7vq5","tags":["x_refsource_CONFIRM"],"url":"https://github.com/discourse/discourse/security/advisories/GHSA-5f9h-vp7v-7vq5"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:663d692e7c0c4b748bf0133e213b6f7056e99886c1c780f5a13f5f7d63c47009 · sha256:4d34da0ddbbc6c87… · /containers/cna/references/0

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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