Vulnerability-Lookup

CVE-2026-49856 (GCVE-0-2026-49856)

Vulnerability from cvelistv5 – Published: 2026-08-13 15:00 – Updated: 2026-08-13 17:27

Title

@jshookmcp/jshook: ICMP probe and traceroute skip local-network SSRF authorization

Summary

@jshookmcp/jshook is an MCP server that gives AI agents tools for JavaScript analysis and security research. In version 0.3.1, he network domain has a central SSRF authorization policy that blocks private, loopback, link-local, and reserved targets unless an explicit authorization object allows private network access. The policy is enforced by raw HTTP/TCP/TLS RTT tools, but the ICMP probe and traceroute tools resolve the target and invoke the native ICMP/traceroute sink directly. An MCP client with access to an active network domain can therefore ask the jshookmcp server to probe internal addresses even when local SSRF access is disabled for the other raw network tools. This exposes an internal reachability and route mapping primitive from the server network position. Version 0.3.2 fixes the issue.

Severity

4.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-13 17:25 UTC

CWE

CWE-918 - Server-Side Request Forgery (SSRF)

Assigner

GitHub_M mitre root

References

2 references

URL	Tags
https://github.com/vmoranv/jshookmcp/security/adv…	x_refsource_CONFIRM
https://github.com/vmoranv/jshookmcp/commit/02111…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
vmoranv	jshookmcp	Affected: = 0.3.1	guessed

Show details on NVD website

JSON

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FKIE_CVE-2026-49856

Vulnerability from fkie_nvd - Published: 2026-08-13 15:19 - Updated: 2026-08-13 18:17

Severity

4.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/vmoranv/jshookmcp/commit/02111311f7bd0f86a7d7ef8538986594b3a18afa
	security-advisories@github.com	https://github.com/vmoranv/jshookmcp/security/advisories/GHSA-c5r6-m4mr-8q5j
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/vmoranv/jshookmcp/security/advisories/GHSA-c5r6-m4mr-8q5j

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "jshookmcp",
          "vendor": "vmoranv",
          "versions": [
            {
              "status": "affected",
              "version": "= 0.3.1"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
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    {
      "lang": "en",
      "value": "@jshookmcp/jshook is an MCP server that gives AI agents tools for JavaScript analysis and security research. In version 0.3.1, he network domain has a central SSRF authorization policy that blocks private, loopback, link-local, and reserved targets unless an explicit authorization object allows private network access. The policy is enforced by raw HTTP/TCP/TLS RTT tools, but the ICMP probe and traceroute tools resolve the target and invoke the native ICMP/traceroute sink directly. An MCP client with access to an active network domain can therefore ask the jshookmcp server to probe internal addresses even when local SSRF access is disabled for the other raw network tools. This exposes an internal reachability and route mapping primitive from the server network position. Version 0.3.2 fixes the issue."
    }
  ],
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  "references": [
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}

GHSA-C5R6-M4MR-8Q5J

Vulnerability from github – Published: 2026-07-01 18:14 – Updated: 2026-07-01 18:14

Summary

@jshookmcp/jshook: ICMP probe and traceroute skip local-network SSRF authorization

Details

Summary

The network domain has a central SSRF authorization policy that blocks private, loopback, link-local, and reserved targets unless an explicit authorization object allows private network access. The policy is enforced by raw HTTP/TCP/TLS RTT tools, but the ICMP probe and traceroute tools resolve the target and invoke the native ICMP/traceroute sink directly.

An MCP client with access to an active network domain can therefore ask the jshookmcp server to probe internal addresses such as 10.0.0.1 even when local SSRF access is disabled for the other raw network tools. This exposes an internal reachability and route mapping primitive from the server network position.

Affected code

Current main https://github.com/vmoranv/jshookmcp/commit/d309c395738638e384c28c0f599b47b2213ab595 and npm package @jshookmcp/jshook 0.3.1 both contain the issue.

src/server/domains/network/handlers/raw-latency-handlers.ts:61-66: network_rtt_measure parses optional authorization and calls resolveAuthorizedTransportTarget before probing.
src/server/domains/network/handlers/raw-latency-handlers.ts:185-190: network_latency_stats uses the same authorization guard.
src/server/domains/network/handlers/raw-latency-handlers.ts:123-139: network_traceroute resolves target with resolveHostname and calls traceroute without an authorization policy check.
src/server/domains/network/handlers/raw-latency-handlers.ts:240-257: network_icmp_probe resolves target with resolveHostname and calls icmpProbe without an authorization policy check.
src/server/domains/network/handlers/raw-latency-handlers.ts:408-416: resolveHostname returns IPv4 literals directly and otherwise performs DNS A lookup without checking private, loopback, link-local, or reserved ranges.
src/utils/network/ssrf-policy.ts:244-316: the central policy blocks private targets unless explicit authorization or ALLOW_LOCAL_SSRF=true is set.

Reproduction

Used a focused regression test against the real handleCallTool and RawHandlers call path with fake native ICMP and policy sinks. The test does not send external traffic. It proves the denied control and the bypass through the same MCP meta-tool dispatch path.

Test file path in my local checkout:

tests/server/security/jshookmcp-network-meta-boundary.test.ts

Relevant test body:

it('denied control: RTT path consults the SSRF authorization guard for private targets', async () => {
  const handler = new RawHandlers();
  state.resolveAuthorizedTransportTarget.mockRejectedValue(new Error('RTT measurement blocked: target resolves to a private or reserved address.'));
  await expect(handler.handleNetworkRttMeasure({ url: 'https://10.0.0.1/', probeType: 'tcp' })).rejects.toThrow(/blocked/);
  expect(state.resolveAuthorizedTransportTarget).toHaveBeenCalled();
  expect(state.icmpProbe).not.toHaveBeenCalled();
});

it('bypass proof: call_tool can drive network_icmp_probe to a private IP without the SSRF authorization guard', async () => {
  const raw = new RawHandlers();
  const ctx = {
    router: { has: vi.fn((name: string) => name === 'network_icmp_probe') },
    executeToolWithTracking: vi.fn((name: string, args: Record<string, unknown>) => raw.handleNetworkIcmpProbe(args)),
  } as any;

  const response = await handleCallTool(ctx, { name: 'network_icmp_probe', args: { target: '10.0.0.1', ttl: 64 } });
  const body = JSON.parse(response.content[0].text);

  expect(body.success).toBe(true);
  expect(ctx.router.has).toHaveBeenCalledWith('network_icmp_probe');
  expect(ctx.executeToolWithTracking).toHaveBeenCalledWith('network_icmp_probe', { target: '10.0.0.1', ttl: 64 });
  expect(state.resolveAuthorizedTransportTarget).not.toHaveBeenCalled();
  expect(state.icmpProbe).toHaveBeenCalledWith(expect.objectContaining({ target: '10.0.0.1', ttl: 64 }));
});

Command run:

corepack pnpm exec vitest run --config vitest.config.ts tests/server/security/jshookmcp-network-meta-boundary.test.ts --reporter=verbose

Result:

Test Files  1 passed (1)
Tests       4 passed (4)

The observed vulnerable call sequence is:

call_tool(name=network_icmp_probe, args={target: 10.0.0.1, ttl: 64})
  -> ctx.router.has(network_icmp_probe) == true
  -> ctx.executeToolWithTracking(network_icmp_probe, validatedArgs)
  -> RawHandlers.handleNetworkIcmpProbe(validatedArgs)
  -> resolveHostname(10.0.0.1) returns 10.0.0.1
  -> icmpProbe({ target: 10.0.0.1, ttl: 64, ... })

resolveAuthorizedTransportTarget is not called on this path. The same missing policy pattern exists for network_traceroute.

Impact

An MCP client with access to the active network domain can use the server as a backend-origin internal network probing oracle. The result can reveal whether internal hosts respond, approximate latency, traceroute hops, and ICMP error classes from the server network position.

The practical impact is strongest when jshookmcp is exposed over Streamable HTTP or another remote transport, multiple clients share one server, or the server runs on Windows or with raw socket capability. This is not code execution and does not by itself exfiltrate response bodies.

Remediation

Apply the same authorization model used by network_rtt_measure and network_latency_stats to network_icmp_probe and network_traceroute. In particular, accept an optional authorization object, resolve the target through the central policy helper or an equivalent host-only policy helper, block private and reserved ranges by default, and pass only the policy-approved resolved address to the native probe. Add regression tests for default-denied private targets, authorized private CIDR access, private hostnames, and call_tool dispatch.

Severity

4.3 (Medium)


                  
                    CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@jshookmcp/jshook"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.3.1"
            },
            {
              "fixed": "0.3.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.3.1"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-49856"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-918"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-01T18:14:57Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nThe network domain has a central SSRF authorization policy that blocks private, loopback, link-local, and reserved targets unless an explicit authorization object allows private network access. The policy is enforced by raw HTTP/TCP/TLS RTT tools, but the ICMP probe and traceroute tools resolve the target and invoke the native ICMP/traceroute sink directly.\n\nAn MCP client with access to an active network domain can therefore ask the jshookmcp server to probe internal addresses such as 10.0.0.1 even when local SSRF access is disabled for the other raw network tools. This exposes an internal reachability and route mapping primitive from the server network position.\n\n## Affected code\n\nCurrent main https://github.com/vmoranv/jshookmcp/commit/d309c395738638e384c28c0f599b47b2213ab595 and npm package @jshookmcp/jshook 0.3.1 both contain the issue.\n\n- src/server/domains/network/handlers/raw-latency-handlers.ts:61-66: network_rtt_measure parses optional authorization and calls resolveAuthorizedTransportTarget before probing.\n- src/server/domains/network/handlers/raw-latency-handlers.ts:185-190: network_latency_stats uses the same authorization guard.\n- src/server/domains/network/handlers/raw-latency-handlers.ts:123-139: network_traceroute resolves target with resolveHostname and calls traceroute without an authorization policy check.\n- src/server/domains/network/handlers/raw-latency-handlers.ts:240-257: network_icmp_probe resolves target with resolveHostname and calls icmpProbe without an authorization policy check.\n- src/server/domains/network/handlers/raw-latency-handlers.ts:408-416: resolveHostname returns IPv4 literals directly and otherwise performs DNS A lookup without checking private, loopback, link-local, or reserved ranges.\n- src/utils/network/ssrf-policy.ts:244-316: the central policy blocks private targets unless explicit authorization or ALLOW_LOCAL_SSRF=true is set.\n\n## Reproduction\n\nUsed a focused regression test against the real handleCallTool and RawHandlers call path with fake native ICMP and policy sinks. The test does not send external traffic. It proves the denied control and the bypass through the same MCP meta-tool dispatch path.\n\nTest file path in my local checkout:\n\n```text\ntests/server/security/jshookmcp-network-meta-boundary.test.ts\n```\n\nRelevant test body:\n\n```ts\nit(\u0027denied control: RTT path consults the SSRF authorization guard for private targets\u0027, async () =\u003e {\n  const handler = new RawHandlers();\n  state.resolveAuthorizedTransportTarget.mockRejectedValue(new Error(\u0027RTT measurement blocked: target resolves to a private or reserved address.\u0027));\n  await expect(handler.handleNetworkRttMeasure({ url: \u0027https://10.0.0.1/\u0027, probeType: \u0027tcp\u0027 })).rejects.toThrow(/blocked/);\n  expect(state.resolveAuthorizedTransportTarget).toHaveBeenCalled();\n  expect(state.icmpProbe).not.toHaveBeenCalled();\n});\n\nit(\u0027bypass proof: call_tool can drive network_icmp_probe to a private IP without the SSRF authorization guard\u0027, async () =\u003e {\n  const raw = new RawHandlers();\n  const ctx = {\n    router: { has: vi.fn((name: string) =\u003e name === \u0027network_icmp_probe\u0027) },\n    executeToolWithTracking: vi.fn((name: string, args: Record\u003cstring, unknown\u003e) =\u003e raw.handleNetworkIcmpProbe(args)),\n  } as any;\n\n  const response = await handleCallTool(ctx, { name: \u0027network_icmp_probe\u0027, args: { target: \u002710.0.0.1\u0027, ttl: 64 } });\n  const body = JSON.parse(response.content[0].text);\n\n  expect(body.success).toBe(true);\n  expect(ctx.router.has).toHaveBeenCalledWith(\u0027network_icmp_probe\u0027);\n  expect(ctx.executeToolWithTracking).toHaveBeenCalledWith(\u0027network_icmp_probe\u0027, { target: \u002710.0.0.1\u0027, ttl: 64 });\n  expect(state.resolveAuthorizedTransportTarget).not.toHaveBeenCalled();\n  expect(state.icmpProbe).toHaveBeenCalledWith(expect.objectContaining({ target: \u002710.0.0.1\u0027, ttl: 64 }));\n});\n```\n\nCommand run:\n\n```bash\ncorepack pnpm exec vitest run --config vitest.config.ts tests/server/security/jshookmcp-network-meta-boundary.test.ts --reporter=verbose\n```\n\nResult:\n\n```text\nTest Files  1 passed (1)\nTests       4 passed (4)\n```\n\nThe observed vulnerable call sequence is:\n\n```text\ncall_tool(name=network_icmp_probe, args={target: 10.0.0.1, ttl: 64})\n  -\u003e ctx.router.has(network_icmp_probe) == true\n  -\u003e ctx.executeToolWithTracking(network_icmp_probe, validatedArgs)\n  -\u003e RawHandlers.handleNetworkIcmpProbe(validatedArgs)\n  -\u003e resolveHostname(10.0.0.1) returns 10.0.0.1\n  -\u003e icmpProbe({ target: 10.0.0.1, ttl: 64, ... })\n```\n\nresolveAuthorizedTransportTarget is not called on this path. The same missing policy pattern exists for network_traceroute.\n\n## Impact\n\nAn MCP client with access to the active network domain can use the server as a backend-origin internal network probing oracle. The result can reveal whether internal hosts respond, approximate latency, traceroute hops, and ICMP error classes from the server network position.\n\nThe practical impact is strongest when jshookmcp is exposed over Streamable HTTP or another remote transport, multiple clients share one server, or the server runs on Windows or with raw socket capability. This is not code execution and does not by itself exfiltrate response bodies.\n\n## Remediation\n\nApply the same authorization model used by network_rtt_measure and network_latency_stats to network_icmp_probe and network_traceroute. In particular, accept an optional authorization object, resolve the target through the central policy helper or an equivalent host-only policy helper, block private and reserved ranges by default, and pass only the policy-approved resolved address to the native probe. Add regression tests for default-denied private targets, authorized private CIDR access, private hostnames, and call_tool dispatch.",
  "id": "GHSA-c5r6-m4mr-8q5j",
  "modified": "2026-07-01T18:14:57Z",
  "published": "2026-07-01T18:14:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/vmoranv/jshookmcp/security/advisories/GHSA-c5r6-m4mr-8q5j"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/vmoranv/jshookmcp"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "@jshookmcp/jshook: ICMP probe and traceroute skip local-network SSRF authorization"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
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Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-49856 (GCVE-0-2026-49856)

FKIE_CVE-2026-49856

GHSA-C5R6-M4MR-8Q5J

Summary

Affected code

Reproduction

Impact

Remediation

Tags

Sightings

Nomenclature