LangBot: Authenticated RCE Via MCP Configuration

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.8 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-54449: 0.72% estimated exploitation activity in the next 30 days; percentile 54.00 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Any authenticated user can achieve arbitrary command execution on the LangBot servers through changing the MCP Server Configuration by added an "STDIO" MCP with an arbitrary command. Details The repository uses StdioServerParameters which is based on Anthropic's modelcontextprotocol open source, inside the code - src/langbot/pkg/provider/tools/loaders/mcp.py - StdioServerParameters is imported from mcp, which executes a given command which runs a subprocess on the target machine. Since the LangBot services are authenticated, an attacker finding an open server needs to sign up or login via stolen credentials, then the attacker can use the MCP configuration to enter any arbitrary command, giving the ability to completely take over the machine. PoC 1. Open the LangBot server 2. Navigate to Extensions 3. Open the "MCP" tab and press "Add" 4. Choose an STDIO server configuration 5. Add any arbitrary command with arguments <img width="480" height="538" alt="Screenshot 2026-01-19 at…

Published by the source

15 Jul 2026, 17:39 UTC

Last modified by the source

23 Jul 2026, 15:11 UTC

Source last checked

26 Oct 2026, 13:46 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-3pvh-63gf-j9mw

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-3pvh-63gf-j9mw

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# Patch Next advisory brief: CVE-2026-54449

Advisory: LangBot: Authenticated RCE Via MCP Configuration
IDs: CVE-2026-54449, GHSA-3pvh-63gf-j9mw
Record: https://patchnext.com/advisories/cve-2026-54449 (revision 2, source checked 26 Oct 2026, 13:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor response not established. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI langbot: affected <= 4.10.5

## Suggested inspection (read-only)
- `python -m pip show langbot`: prints the installed version. Run with the environment that serves production active.

## Supported action
No complete vendor fix is recorded. Follow the primary source's mitigation guidance and check this record again before closing anything.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on langbot.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-3pvh-63gf-j9mw (OSV record GHSA-3pvh-63gf-j9mw lists affected ranges: PyPI langbot >=0 <=4.10.5)
- Verified: https://github.com/advisories/GHSA-3pvh-63gf-j9mw (GitHub-reviewed advisory GHSA-3pvh-63gf-j9mw lists affected ranges: PyPI langbot >=0 <=4.10.5)

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