atomic-agents-stack: HTTP MCP catalog accepts cleartext http and spawns catalog-supplied commands (MITM to RCE)

Exploitation

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

CVSS 4.0

8.7 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

The HTTP MCP server-registry backend factory (atomicagents/mcpregistry/http.py, makehttpmcpserverregistrybackendfromurl) accepts both http and https schemes. Catalog entries carry command/args that are type-validated but content-unrestricted, and are later spawned as local stdio subprocesses by MCPClientPool. Over a cleartext http:// catalog URL, a network man-in-the-middle can rewrite the catalog response to inject an arbitrary command/args and obtain code execution on the agent host, with no LLM involvement. The Policy MCP allowlist is not a default mitigation (mcpallowfn defaults to None), so absent an operator-authored allowlist every resolved spec connects. Affected: mcpregistry/http.py, all versions through 1.0.0. (The https path is sound: httpx defaults to verify=True, followredirects=False.) Fix: require https by default and gate http:// behind a loud explicit opt-in. Defense-in-depth: allowlist the resolved command basename (or require confirmation) before any…

Published by the source

17 Aug 2026, 21:49 UTC

Last modified by the source

17 Aug 2026, 21:49 UTC

Source last checked

26 Oct 2026, 13:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xhcr-cqfr-m3hv

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# Patch Next advisory brief: GHSA-xhcr-cqfr-m3hv

Advisory: atomic-agents-stack: HTTP MCP catalog accepts cleartext http and spawns catalog-supplied commands (MITM to RCE)
IDs: GHSA-xhcr-cqfr-m3hv
Record: https://patchnext.com/advisories/ghsa-xhcr-cqfr-m3hv (revision 1, source checked 26 Oct 2026, 13:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: atomic-agents-stack 1.1.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI atomic-agents-stack: affected <= 1.0.0; fixed in 1.1.0

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

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on atomic-agents-stack.
- 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://github.com/advisories/GHSA-xhcr-cqfr-m3hv (GitHub-reviewed advisory GHSA-xhcr-cqfr-m3hv lists affected ranges: PyPI atomic-agents-stack >=0 <=1.0.0)

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