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PatchSiren cyber security CVE debrief

CVE-2026-44559 open-webui CVE debrief

A missing authorization check in Open WebUI's channel member enumeration endpoint allows authenticated users to list members of private channels without access. The GET /api/v1/channels/{id}/members endpoint only validates membership for group and direct message channels, leaving standard channels—including private ones—unprotected. Any authenticated user with knowledge of a private channel's UUID can retrieve its complete member list. This information disclosure vulnerability has a CVSS 3.1 score of 4.3 (Medium) and was resolved in version 0.9.0.

Vendor
open-webui
Product
Unknown
CVSS
MEDIUM 4.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-15
Original CVE updated
2026-05-19
Advisory published
2026-05-15
Advisory updated
2026-05-19

Who should care

Organizations running self-hosted Open WebUI instances below version 0.9.0, particularly those relying on private channels for sensitive collaboration. Security teams should prioritize patching and log review for environments with strict channel privacy requirements.

Technical summary

The vulnerability exists in the channel member retrieval API endpoint. The application checks channel_has_access only for 'group' and 'dm' channel types, while 'standard' channel types—including private channels—bypass this validation. An authenticated attacker can supply any valid channel UUID to enumerate members without membership in that channel. The fix in 0.9.0 extends access control checks to all channel types.

Defensive priority

medium

Recommended defensive actions

  • Upgrade Open WebUI to version 0.9.0 or later to obtain the authorization fix
  • Review channel access patterns in application logs for unauthorized member enumeration attempts
  • Audit private channel UUID exposure in client-side code, browser history, or shared links that could facilitate targeted enumeration
  • Implement additional network-level access controls or API rate limiting for channel member endpoints as defense in depth
  • Verify that custom channel implementations or forks include equivalent access control checks for all channel types

Evidence notes

Vulnerability confirmed through vendor security advisory and NVD analysis. The issue stems from incomplete access control logic at lines 467-469 of the affected endpoint implementation.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-44559 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-44559

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

  • CVE-2026-44559 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-44559

    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.