ContextForge: DNS TOCTOU race condition causes SSRF protection bypass (/admin/gateways/test)

Exploitation

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

CVSS

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

EPSS

• CVE-2026-53708: 0.35% estimated exploitation activity in the next 30 days; percentile 28.69 (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 The /admin/gateways/test endpoint validates submitted URLs by resolving the hostname at validation time and blocking private address ranges. The HTTP client independently re-resolves DNS at connection time with no IP binding between the two operations, creating a TOCTOU window exploitable via DNS rebinding. The source code explicitly acknowledges this limitation in two separate locations. Details validategatewaytesturl() in mcpgateway/common/validators.py (lines 1527–1710) calls socket.getaddrinfo() on the submitted hostname, checks whether the resolved IP falls in private, loopback, link-local, or cloud-metadata ranges (including 169.254.169.254, 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16), and accepts the URL if the result is clean. The validated URL is then passed to the HTTP client as the original hostname string, not as the validated IP address. The HTTP client (httpx, via ResilientHttpClient) performs its own independent DNS resolution at connection time. No…

Published by the source

14 Aug 2026, 19:49 UTC

Last modified by the source

14 Aug 2026, 19:49 UTC

Source last checked

26 Oct 2026, 13:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-9hgc-g3w5-67cm

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# Patch Next advisory brief: CVE-2026-53708

Advisory: ContextForge: DNS TOCTOU race condition causes SSRF protection bypass (`/admin/gateways/test`)
IDs: CVE-2026-53708, GHSA-9hgc-g3w5-67cm
Record: https://patchnext.com/advisories/cve-2026-53708 (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: Medium (CVSS 6.6)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: mcp-contextforge-gateway 1.0.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI mcp-contextforge-gateway: affected < 1.0.3; fixed in 1.0.3

## Suggested inspection (read-only)
- `python -m pip show mcp-contextforge-gateway`: 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 mcp-contextforge-gateway.
- 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-9hgc-g3w5-67cm (GitHub-reviewed advisory GHSA-9hgc-g3w5-67cm lists affected ranges: PyPI mcp-contextforge-gateway >=0 <1.0.3)

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