Authorization Flaw in open-webu (CVE-2026-45339)
Summary
Vulnerability in open-webu (CVE-2026-45339). Confidential information can be exposed externally. Exploitable via Authorization header. Mitigation: upgrade to 0.9.0 or later.
Original description
The description as published by the source.
Summary
Open WebUI allows admins to restrict which API endpoints an API key can access. When an API key is restricted from /api/v1/messages, requests using the Authorization: Bearer sk-... header are correctly blocked with 403. However, the same key sent via the x-api-key header bypasses the restriction entirely — the request is authenticated, the model is invoked, and a full response is returned.
Details
Open WebUI's Anthropic-compatible API path accepts authentication via x-api-key header (standard for the Anthropic API). The endpoint restriction check only applies to keys presented via the Authorization header. When the same sk-... key is supplied in x-api-key, the restriction check is skipped but the key is still valid for authentication.
This means any API key, regardless of its configured endpoint restrictions, can access any API endpoint by simply using x-api-key instead of Authorization.
PoC
Verified against Open WebUI v0.8.11.
Setup: Admin creates a user with an API key that has endpoint restrictions (not allowed on /api/v1/messages). A mock OpenAI-compatible model (mock-model) is configured.
API_KEY="sk-dc56016d720e49ba9e95584d602b79bb"
# Test 1: Authorization header — BLOCKED (endpoint restriction enforced)
curl -s -X POST http://target:8080/api/v1/messages \
-H "Authorization: Bearer $API_KEY" \
-H 'Content-Type: application/json' \
-d '{"model":"mock-model","messages":[{"role":"user","content":"via…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-45339 has been found in open-webu.
Attackers can target a specific entry point like Authorization header over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 6.5/10.
What to do: upgrade open-webu to 0.9.0 or later.
If unsure, ask your IT team or search "open-webu CVE-2026-45339" on the vendor's site.
CVE-2026-45339 (open-webu) — CWE-863 / CVSS v3 6.5
Attack vector: remote (network-reachable) / no user interaction
Attack surface: Authorization header / X-API-Key header / Authorization
Patched: 0.9.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Incorrect authorization (CWE-863) exists in open-webu. Attackers reach the vulnerable code path via Authorization header.
Check the vendor advisory for the affected versions of open-webu. Attack surface: Authorization header / X-API-Key header / Authorization.
Severity: Medium (CVSS 6.5/10). Confidential information can be exposed externally.
Update to 0.9.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'open-webu' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'open-webu' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
open-webuを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade open-webu to 0.9.0ステージング環境で 0.9.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- package pypi.org
- web github.com
- web github.com