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Fencer Vulns
medium 6.6

CVE-2026-53708 json

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

published 2026-08-14 2 mo ago modified 2026-09-30 39 d ago also GHSA-9hgc-g3w5-67cm , PYSEC-2026-3684 , EUVD-2026-77591

cvss
6.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 28%
public exploits
0
none known

Summary

ContextForge is an AI gateway, registry, and proxy that provides centralized discovery, guardrails, and management for MCP, A2A, and REST or gRPC APIs. Prior to 1.0.3, the /admin/gateways/test call site in mcpgateway/admin.py calls validate_gateway_test_url() in mcpgateway/common/validators.py to resolve and reject private, loopback, link-local, and cloud-metadata addresses, but ResilientHttpClient later resolves the original hostname again without binding the validated address. When MCPGATEWAY_ADMIN_API_ENABLED is enabled, an attacker with a database-backed role containing explicit gateways.read permission can use DNS rebinding to return a public address during validation and a private or metadata address during connection, bypassing ssrf_blocked_networks and ssrf_dns_fail_closed because those controls apply only to the validation-time result. The endpoint's allow_admin_bypass=False setting means a bootstrap-only virtual platform-admin identity without a database role is not sufficient. Successful exploitation can reach internal services and cloud metadata, expose cloud credentials, access internal APIs, or probe internal network ports. This issue is fixed in version 1.0.3.

Patch / fix

  • pypi mcp-contextforge-gateway 1.0.3

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
55 d ago

Exploit prediction

0.35% chance of exploitation in the next 30 days, higher than 28% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/IBM/mcp-context-forge/security/advisories/GHSA-9hgc-g3w5-67cm referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.6 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:L/A:N
OSV 3.1 6.6 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:L/A:N
GitHub 3.1 6.6 CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:C/C:H/I:L/A:N

Affected packages

ecosystem package affected fixed in
pypi mcp-contextforge-gateway
<1.0.3
1.0.3

Affected products

  • IBM mcp-context-forge
  • IBM mcp-contextforge-gateway

Classification

Weakness
  • CWE-350 Reliance on Reverse DNS Resolution for a Security-Critical Action
  • CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition
  • CWE-918 Server-Side Request Forgery

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.