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Vulnerabilities

Vulnerability · CVE-2026-120492

Chainlist has SSRF via MCP SSE and streamable-http transports that allows unauthenticated internal network access

Published Aug 25, 2026 · catalog updated Nov 3, 2026 · Chainlist has SSRF via

Last checked Nov 4, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-120492. EPSS is 0.22%. Act only if a listed version of Chainlist has SSRF via is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Chainlist has SSRF via).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.2
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.22%
Remediation
Advisory link
Affected products
PyPI chainlit

### Am I affected? Only if your deployment sets in . **MCP has been disabled by default since v2.7.0**, so most Chainlit deployments are not affected. No authentication is required: is reachable by any client that can open a session. ### Summary When MCP is enabled ( ), the endpoint for and transports accepts a user-controlled and optional 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 and . ### Affected / patched versions | | | |---|---| | CVE | CVE-2026-45019 | | Affected — URL-based SSRF | (sink present since MCP support was introduced, PR #1977) | | Affected — attacker-controlled header forwarding (amplifies the above) | (added in PR #2292) | | Patched | **2.12.0** (releasing 2026-08-25) | ### Details The Pydantic request models in define as a bare with no scheme check, no private IP filtering, and no allowlist. When is or , the handler in passes the URL and headers directly to the MCP SDK's or , which make outbound HTTP requests from the server. The SSE URL sink has existed since MCP support was first introduced in v2.4.0rc0 (PR #1977). PR #2292 (merged 2025-07-30, released in v2.6.4) added support and introduced attacker-controlled forwarding for both transports. This amplified the SSRF from a simple URL-based request to one where the attacker can set arbitrary HTTP headers like and . This is a blind SSRF: the server makes the outbound request, but the response is consumed internally by the MCP client and never returned to the attacker. In cloud environments, an attacker could probe metadata endpoints (e.g., 169.254.169.254). **Vulnerable code:** — handler **Sink:** — / ### PoC Tested against Chainlit 2.11.0 with and a local TCP listener. 1. Start a listener to capture the server-side request: 2. Establish a Socket.IO session and trigger the SSRF: 3. The

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • PyPI chainlit2.4.0rc0 → 2.12.0

How to fix CVE-2026-120492

  • Upgrade

    CVE-2026-120492 lists a fix boundary at 2.12.0. Compare the installed build with that boundary before you change production.

  • Version check

    Seen in 2.4.0rc0 → 2.12.0

  • Advisory

    Open the cve_org record and follow its fix.

  • Official advisories

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-120492. EPSS is 0.22%. Act only if a listed version of Chainlist has SSRF via is installed.

Which versions are affected?

Compare what you have installed with 2.4.0rc0 → 2.12.0. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-918: Server-Side Request Forgery (SSRF). EPSS 0.22%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Aug 25, 2026 · PyPA Advisory Database

    Detected

    ### Am I affected? Only if your deployment sets in . **MCP has been disabled by default since v2.7.0**, so most Chainlit deployments are not affected. No authentication is required: is reachable by any client that can open a session. ### Summary When MCP is enabled ( ), the endpoint for and transports accepts a user-controlled and optional dictionary without any validation. An unauthenticated atta

  2. Nov 3, 2026 · PyPA Advisory Database

    Fix available

    chainlit fixed in 2.12.0

  3. Nov 3, 2026 · PyPA Advisory Database

    Fix available

    chainlit fixed in 2.12.0

  4. Nov 3, 2026 · PyPA Advisory Database

    Updated

    ### Am I affected? Only if your deployment sets in . **MCP has been disabled by default since v2.7.0**, so most Chainlit deployments are not affected. No authentication is required: is reachable by any client that can open a session. ### Summary When MCP is enabled ( ), the endpoint for and transports accepts a user-controlled and optional dictionary without any validation. An unauthenticated atta

Sources

  • CVE.orgVulnerability recordCVE-2026-120492

    Official CVE identifier

    cve.org
  • PyPA Advisory DatabasePackage advisoryGHSA-hvfh-5mj3-5f3j

    Chainlist has SSRF via MCP SSE and streamable-http transports that allows unauthenticated internal network access

    osv.dev

References

Freshness

Last verified in this catalog Nov 4, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgNov 4, 2026
  • PyPA Advisory DatabaseNov 4, 2026