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PatchSiren cyber security CVE debrief

CVE-2026-45386 open-webui CVE debrief

Open WebUI versions prior to 0.9.5 contain an authorization bypass vulnerability in the message pinning functionality. The Pin/Unpin operation modifies message state (is_pinned, pinned_by, pinned_at fields) but incorrectly validates only read permissions in standard channels. This allows users with read-only access to pin or unpin any message, violating the expected write-access control boundary. The vulnerability has a CVSS 3.1 score of 4.3 (Medium severity) with an attack vector of network-accessible, low attack complexity, and low privileges required. No user interaction is needed, and the impact is limited to integrity (low) with no confidentiality or availability impact. The issue is classified under CWE-639: Authorization Bypass Through User-Controlled Key. The vendor has released version 0.9.5 to remediate this flaw. No known exploitation in the wild or ransomware campaign use has been reported.

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 with multi-user channel configurations, particularly those relying on read-only permissions to restrict user capabilities in shared AI conversation spaces.

Technical summary

The vulnerability exists in the Pin/Unpin API endpoint for standard channels. The endpoint performs a permission check using read-level authorization rather than write-level authorization. When a user with read-only channel access submits a pin or unpin request, the insufficient check permits the operation to proceed, updating the message's pinned status, pinner identity, and timestamp fields. This represents a horizontal privilege escalation where read access is incorrectly treated as sufficient for state-modifying operations. The fix in 0.9.5 implements proper write permission validation before allowing pin state modifications.

Defensive priority

medium

Recommended defensive actions

  • Upgrade Open WebUI to version 0.9.5 or later to remediate the authorization bypass vulnerability
  • Review channel permission configurations to ensure write operations require appropriate authorization checks
  • Audit message pin/unpin history in standard channels for unauthorized modifications if running affected versions
  • Monitor access logs for anomalous pinning activity from read-only user accounts
  • Validate that custom permission implementations do not replicate the same read-only check for write operations

Evidence notes

Vulnerability confirmed through vendor security advisory (GHSA-5gc6-xhv4-2wg6) and NVD record. CPE criteria confirms affected versions are all releases prior to 0.9.5. CVSS vector and CWE classification sourced from official vulnerability databases.

Official resources

2026-05-15T21:16:37.043Z