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

> Unauthenticated attackers can trigger Server-Side Request Forgery in Chainlit when MCP is enabled, accessing internal networks and metadata endpoints.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Aug 2026
- **Updated:** 27 Aug 2026
- **Also known as:** GHSA-hvfh-5mj3-5f3j, PYSEC-2026-3811

## What is CVE-2026-45019?

CVE-2026-45019 is a high-severity server-side request forgery vulnerability in chainlit, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-918 (Server-Side Request Forgery)

## Which versions are affected by CVE-2026-45019?

3 open source packages ship an affected version, including chainlit.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `chainlit` | PyPI | From 2.4.0rc0 | 2.12.0 |
| `chainlit` | PyPI | From 2.4.0rc0 | 2.12.0 |
| `chainlit` | PyPI | From 2.4.0rc0 | 2.12.0 |

## How do I fix CVE-2026-45019?

Upgrade chainlit to 2.12.0 or later.

## Is CVE-2026-45019 being exploited?

There is no known exploitation of CVE-2026-45019 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-45019 and fix it if it is affected.

What it is: CVE-2026-45019 is a high-severity server-side request forgery vulnerability in chainlit, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-45019 in the wild and no public exploit code.

Affected packages and fixed versions:
- chainlit (PyPI): affected from 2.4.0rc0; fixed in 2.12.0
- chainlit (PyPI): affected from 2.4.0rc0; fixed in 2.12.0
- chainlit (PyPI): affected from 2.4.0rc0; fixed in 2.12.0

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-45019/ (Markdown: https://insights.sbomify.com/CVE-2026-45019/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-45019
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-45019
- OSV: https://osv.dev/vulnerability/CVE-2026-45019

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-45019/
Summaries are generated and may contain mistakes; the official description above is the record.