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CVE-2026-45339 open-webui CVE debrief

Open WebUI versions prior to 0.9.0 contain an authorization bypass vulnerability in API key endpoint restrictions. When administrators configure API keys with restricted endpoint access, the restriction is properly enforced for requests using the `Authorization: Bearer sk-...` header format, returning HTTP 403 Forbidden. However, identical API keys submitted via the `x-api-key` header bypass these restrictions entirely, allowing authenticated access to restricted endpoints including `/api/v1/messages`, with full model invocation and response generation. This flaw represents a case of inconsistent authorization enforcement across authentication pathways (CWE-863). The vulnerability was disclosed on 2026-05-15 and last modified on 2026-05-19. Organizations running affected versions should upgrade to Open WebUI 0.9.0 or later to remediate this issue.

Vendor
open-webui
Product
Unknown
CVSS
MEDIUM 6.5
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 self-hosting Open WebUI for offline AI operations, particularly those relying on API key endpoint restrictions for access control or compliance purposes.

Technical summary

The vulnerability stems from incomplete authorization logic that validates endpoint restrictions for Bearer token authentication but fails to apply identical checks when the same API key is presented via the x-api-key header. This allows privilege escalation where restricted API keys gain unauthorized access to blocked endpoints. The fix in version 0.9.0 unifies authorization enforcement across both authentication pathways.

Defensive priority

medium

Recommended defensive actions

  • Upgrade Open WebUI to version 0.9.0 or later to remediate the authorization bypass vulnerability.
  • Review API key configurations and access logs for unauthorized endpoint access via x-api-key header prior to upgrade.
  • Verify that endpoint restrictions are consistently enforced across all authentication header formats after upgrading.
  • Consider implementing additional network-layer controls or API gateway policies to enforce endpoint restrictions as defense in depth.

Evidence notes

Vendor advisory confirms bypass mechanism and fix version; NVD analysis confirms CVSS 3.1 vector and affected version range.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-45339 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-45339

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

  • CVE-2026-45339 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-45339

    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.