SSRF (Server-Side Request Forgery) in chainlit (CVE-2026-45019)
Summary
SSRF in chainlit (CVE-2026-45019). Risk of unauthorized operations or information disclosure. Exploitable via POST /mcp. Mitigation: upgrade to 2.12.0 or later.
Original description
The description as published by the source.
Am I affected?
Only if your deployment sets features.mcp.enabled = true in .chainlit/config.toml. MCP has been disabled by default since v2.7.0, so most Chainlit deployments are not affected. No authentication is required: /mcp is reachable by any client that can open a session.
Summary
When MCP is enabled (features.mcp.enabled = true), the POST /mcp endpoint for sse and streamable-http transports accepts a user-controlled url and optional headers dictionary without any validation. An unauthenticated attacker can force the Chainlit server to make outbound HTTP requests to arbitrary URLs — including internal network services and cloud metadata endpoints — with attacker-controlled HTTP headers such as Authorization and Cookie.
Affected / patched versions
| CVE | CVE-2026-45019 |
| Affected — URL-based SSRF | >=2.4.0rc0, <2.12.0 (sink present since MCP support was introduced, PR #1977) |
| Affected — attacker-controlled header forwarding (amplifies the above) | >=2.6.4, <2.12.0 (added in PR #2292) |
| Patched | 2.12.0 (releasing 2026-08-25) |
Details
The Pydantic request models in backend/chainlit/types.py define url as a bare str with no scheme check, no private IP filtering, and no allowlist. When clientType is "sse" or "streamable-http", the handler in backend/chainlit/server.py passes the URL and headers directly to the MCP SDK's sse_client() or streamablehttp_client(), which make outb…
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-2026-45019 has been found in chainlit.
Attackers can target a specific entry point like POST /mcp over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.2/10.
What to do: upgrade chainlit to 2.12.0 or later.
If unsure, ask your IT team or search "chainlit CVE-2026-45019" on the vendor's site.
CVE-2026-45019 (chainlit) — CWE-918 / CVSS v3 7.2
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: POST /mcp / POST /internal-admin / GET /project/settings / sse
Patched: 2.12.0 — apply immediately
Workaround: set features.mcp.: enabled
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.
SSRF (CWE-918) exists in chainlit. Attackers reach the vulnerable code path via POST /mcp without authentication.
Check the vendor advisory for the affected versions of chainlit. Attack surface: POST /mcp / POST /internal-admin / GET /project/settings / sse.
Severity: High (CVSS 7.2/10). Risk of unauthorized operations or information disclosure.
Update to 2.12.0.
Workaround: set features.mcp.: enabled
Search webserver/proxy logs for unusual POST /mcp requests with malformed payloads or SQL meta-characters. Run grep -r 'chainlit' . 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
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1Identify exposure identify
grep -r 'chainlit' . | 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
chainlit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 /mcp' /var/log/nginx/access.log | grep -E '(unusual_payload|sqli_pattern)'アクセスログで
POST /mcp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 temporary workaround mitigate
set features.mcp.: enabledパッチが適用されるまでの応急処置として、set features.mcp.: enabled を実施。回避策の副作用 (機能低下) を確認した上で。
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4Apply patch patch
Upgrade chainlit to 2.12.0ステージング環境で 2.12.0 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。
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5Post-deployment verification verify
Replay attack against POST /mcp 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。