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Vulnerabilities

Vulnerability · CVE-2026-31869

Discourse is an open-source discussion platform.

Published Mar 20, 2026 · catalog updated Jun 17, 2026 · Discourse is an open-source

Check if you run it

No confirmed exploitation is on record for CVE-2026-31869. EPSS is 0.31%. Act only if a listed version of Discourse is an open-source is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Discourse is an open-source).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium5.3
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.31%
Remediation
Advisory link
Affected products
cpe discourse/discourse

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-latest.1, 2026.2.1, and 2026.1.2 contain a patch. To work around this issue, restrict the messageable policy of any hidden-membership group to staff or group members only, so untrusted users cannot reach the vulnerable code path.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe discourse/discourse2026.3.0

How to fix CVE-2026-31869

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-31869. EPSS is 0.31%. Act only if a listed version of Discourse is an open-source is installed.

Which versions are affected?

Compare what you have installed with 2026.3.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-200: Exposure of Sensitive Information; CWE-285: Improper Authorization; CWE-639: Authorization Bypass Through User-Controlled Key. EPSS 0.31%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 20, 2026 · NIST NVD

    Detected

    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 ret

  2. Jun 17, 2026 · NIST NVD

    Updated

    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 ret

Sources

  • CVE.orgVulnerability recordCVE-2026-31869

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-31869

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-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 hid

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.