Authorization Flaw in open-webui (CVE-2026-54021)
Summary
Vulnerability in open-webui (CVE-2026-54021). Risk of unauthorized operations or information disclosure. Exploitable via POST /ollama/api/chat/{url_idx}. Mitigation: upgrade to >= 0.9.6 or later.
Original description
The description as published by the source.
Summary
Several direct, index-addressed Ollama proxy routes accept a caller-supplied url_idx
path parameter and use it as a raw index into the admin-configured OLLAMA_BASE_URLS
list. Access control on these routes validates only whether the user may use the
requested model, never which backend the request is routed to. Any authenticated
user can append an arbitrary url_idx to force their request onto an Ollama backend
they were never authorized to reach, including internal, higher-privilege, or
explicitly admin-disabled backends.
Affected endpoints
All indexed Ollama routes that resolve the backend through get_ollama_url():
POST /ollama/api/chat/{url_idx}
POST /ollama/api/generate/{url_idx}
POST /ollama/api/embed/{url_idx}
POST /ollama/api/embeddings/{url_idx}
POST /ollama/v1/chat/completions/{url_idx}
POST /ollama/v1/completions/{url_idx}
POST /ollama/v1/messages/{url_idx}
POST /ollama/v1/responses/{url_idx}
Root cause
backend/open_webui/routers/ollama.py — get_ollama_url() consults the
model-to-backend allow-list (OLLAMA_MODELS[model]["urls"]) only when url_idx is
omitted. When the caller supplies url_idx, that mapping is skipped and the value is
used directly as an index:
async def get_ollama_url(request: Request, model: str, url_idx: Optional[int] = None):
if url_idx is None:
models = request.app.state.OLLAMA_MODELS
if model not in models:
raise HTTPException(...)
url_idx = ran…
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-2026-54021 has been found in open-webui.
Attackers can target a specific entry point like POST /ollama/api/chat/{url_idx} over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.3/10.
What to do: upgrade open-webui to >= 0.9.6 or later.
If unsure, ask your IT team or search "open-webui CVE-2026-54021" on the vendor's site.
CVE-2026-54021 (open-webui) — CWE-863 / CVSS v3 6.3
Attack vector: remote (network-reachable) / no user interaction
Attack surface: POST /ollama/api/chat/{url_idx} / POST /ollama/api/generate/{url_idx} / POST /ollama/api/embed/{url_idx} / POST /ollama/api/embeddings/{url_idx}
Patched: >= 0.9.6 — 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-webui. Attackers reach the vulnerable code path via POST /ollama/api/chat/{url_idx}.
Check the vendor advisory for the affected versions of open-webui. Attack surface: POST /ollama/api/chat/{url_idx} / POST /ollama/api/generate/{url_idx} / POST /ollama/api/embed/{url_idx} / POST /ollama/api/embeddings/{url_idx}.
Severity: Medium (CVSS 6.3/10). Risk of unauthorized operations or information disclosure.
Update to >= 0.9.6.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual POST /ollama/api/chat/{url_idx} requests with malformed payloads or SQL meta-characters. Run grep -r 'open-webui' . 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-webui' . | 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-webuiを grep し、稼働しているサービス・バージョンを把握する。 -
2Hunt for indicators of compromise detect
grep 'POST /ollama/api/chat/{url_idx}' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /ollama/api/chat/{url_idx}への異常なリクエスト (不正な認証ヘッダ・SQLメタ文字)を過去 30〜90日分捜索。WAF/SIEM があれば該当パスのアラート発火履歴を確認。 -
3Apply patch patch
Upgrade open-webui to >= 0.9.6ステージング環境で >= 0.9.6 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と、Step 2 で見つけた異常検知の続報チェックを含めること。
-
4Post-deployment verification verify
Replay attack against POST /ollama/api/chat/{url_idx} on staging to confirm patch closes the vector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 Step 2 と同じログクエリ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
- web github.com
- web github.com
- web pypi.org