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CVE-2026-45019— Chainlit: SSRF via MCP SSE and streamable-http transports allows unauthenticated internal network access

Quick assessment

Affected
Chainlit chainlit
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Chainlit是chainlit组织开源的一个大模型对话界面框架。 Chainlit 2.4.0rc0至2.12.0之前版本存在服务端请求伪造漏洞，该漏洞源于接受用户控制的url和headers字典时缺乏方案验证、私有地址过滤或白名单，可能导致攻击者利用服务器发起盲出站请求，发现内部服务、扫描端口、探测元数据端点。

CVSS 7.2 · High EPSS 0.43% · P38

Affected Version Matrix 1

VendorProduct Version RangeStatus
Chainlit chainlit >= 2.4.0rc0, < 2.12.0 affected
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I. Basic Information for CVE-2026-45019

Vulnerability Information
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Vulnerability Title
Chainlit: SSRF via MCP SSE and streamable-http transports allows unauthenticated internal network access
Source: CVE Program / CVE List V5
Vulnerability Description
Chainlit is a Python framework for building production-ready conversational AI applications. From 2.4.0rc0 until 2.12.0, Chainlit deployments with features.mcp.enabled set to true in .chainlit/config.toml expose the POST /mcp endpoint without requiring authentication. For sse and streamable-http transports, ConnectSseMCPRequest and ConnectStreamableHttpMCPRequest in backend/chainlit/types.py accept a user-controlled url and optional headers dictionary without scheme validation, private-address filtering, or an allowlist. The connect_mcp handler in backend/chainlit/server.py passes these values to sse_client() or streamablehttp_client(), allowing the Chainlit server to make blind outbound requests to arbitrary internal or external services, including cloud metadata endpoints, with attacker-controlled Authorization and Cookie headers. The SSE URL sink has existed since 2.4.0rc0, while attacker-controlled header forwarding and streamable-http support were added in 2.6.4. The response is consumed internally and not returned, but the attacker can issue state-changing authenticated requests, discover internal services, scan ports, and probe metadata endpoints. This issue is fixed in version 2.12.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
服务端请求伪造(SSRF)
Source: CVE Program / CVE List V5
Vulnerability Title
Chainlit 服务端请求伪造漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Chainlit是chainlit组织开源的一个大模型对话界面框架。 Chainlit 2.4.0rc0至2.12.0之前版本存在服务端请求伪造漏洞，该漏洞源于接受用户控制的url和headers字典时缺乏方案验证、私有地址过滤或白名单，可能导致攻击者利用服务器发起盲出站请求，发现内部服务、扫描端口、探测元数据端点。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Chainlit chainlit >= 2.4.0rc0, < 2.12.0 -

II. Public POCs for CVE-2026-45019

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 11558 chars
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III. Intelligence Information for CVE-2026-45019

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Vendor Advisories for CVE-2026-45019 (2)

Vendor Pages for CVE-2026-45019 (1)

IV. Related Vulnerabilities

Same product: chainlit
Same vendor: Chainlit
Same weakness: CWE-918