Contentful MCP Server: export_space/import_space tools pass LLM-controlled host/proxy args to CMA client, redirecting server PAT to attacker-controlled endpoint

Exploitation

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

CVSS

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

EPSS

• CVE-2026-53957: 0.41% estimated exploitation activity in the next 30 days; percentile 35.87 (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 exportspace and importspace tools in @contentful/mcp-tools accept LLM-controlled host and proxy parameters that are spread directly into the options object passed to contentful-export / contentful-import. These libraries pass the merged options — including the attacker-controlled host — to the Contentful Management API (CMA) SDK, which builds baseURL from host and attaches the server's CMA Personal Access Token as Authorization: Bearer <PAT on every outgoing request. An attacker who can invoke MCP tools, or inject instructions into Contentful content the LLM reads, can redirect all CMA requests — and the PAT — to an attacker-controlled endpoint. --- Details Root cause — exportSpace.ts lines 126–141 (identical pattern in importSpace.ts lines 103–119): createClientConfig (defined in utils/tools.ts) extracts only accessToken and ignores config.host. The CONTENTFULHOST environment variable is never applied to exportOptions. The downstream chain once contentful-export receives the…

Published by the source

19 Aug 2026, 19:17 UTC

Last modified by the source

19 Aug 2026, 19:33 UTC

Source last checked

26 Oct 2026, 13:01 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-2xhg-73j7-rrgx

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-2xhg-73j7-rrgx

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# Patch Next advisory brief: CVE-2026-53957

Advisory: Contentful MCP Server: export_space/import_space tools pass LLM-controlled `host`/`proxy` args to CMA client, redirecting server PAT to attacker-controlled endpoint
IDs: CVE-2026-53957, GHSA-2xhg-73j7-rrgx
Record: https://patchnext.com/advisories/cve-2026-53957 (revision 2, source checked 26 Oct 2026, 13:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @contentful/mcp-tools 0.4.5; @contentful/mcp-server 1.7.19. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @contentful/mcp-tools: affected < 0.4.5; fixed in 0.4.5
- npm @contentful/mcp-server: affected < 1.7.19; fixed in 1.7.19

## Suggested inspection (read-only)
- `npm ls @contentful/mcp-tools --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls @contentful/mcp-server --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## 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 @contentful/mcp-tools, @contentful/mcp-server.
- 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-2xhg-73j7-rrgx (OSV record GHSA-2xhg-73j7-rrgx lists affected ranges: npm @contentful/mcp-server >=0 =0 <0.4.5 (fixed))
- Verified: https://github.com/advisories/GHSA-2xhg-73j7-rrgx (GitHub-reviewed advisory GHSA-2xhg-73j7-rrgx lists affected ranges: npm @contentful/mcp-server >=0 =0 <0.4.5)

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