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CVE-2026-33300 discourse CVE debrief

CVE-2026-33300 is an authorization bypass vulnerability in Discourse, a popular open-source discussion platform. The vulnerability affects versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0. The issue allows moderators to access information on hidden groups, including their names and user counts, via the Category Chatables Controller show action. The vulnerability has a CVSS score of 5.3 and a severity of MEDIUM. The issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.

Vendor
discourse
Product
Unknown
CVSS
MEDIUM 5.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-03-31
Original CVE updated
2026-07-24
Advisory published
2026-03-31
Advisory updated
2026-07-24

Who should care

System administrators and security teams responsible for managing Discourse installations should be aware of this vulnerability. Specifically, those using affected versions of Discourse should prioritize patching to prevent potential misuse of moderator privileges. Additionally, security teams should review and restrict moderator privileges, and monitor for suspicious activity related to hidden groups.

Technical summary

The vulnerability is caused by an authorization bypass in the Category Chatables Controller show action. This allows moderators to access sensitive information about hidden groups, including their names and user counts. The issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0. The vulnerability has a CVSS score of 5.3 and a severity of MEDIUM. The affected product is Discourse, a popular open-source discussion platform.

Defensive priority

Medium

Recommended defensive actions

  • Apply patches or updates to affected Discourse versions
  • Review and restrict moderator privileges
  • Monitor for suspicious activity related to hidden groups
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-03-31T18:16:52.267Z and last modified on 2026-07-24T20:10:00.147Z. The NVD entry is currently Analyzed. The vulnerability affects Discourse versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0. There is limited information available about the vulnerability from the source, and defenders should verify the affected scope and severity with the vendor. The CVE record and NVD entry provide the most accurate and up-to-date information.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-33300 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-33300

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-33300 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-33300

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.