Vulnerability-Lookup

CVE-2026-49411 (GCVE-0-2026-49411)

Vulnerability from cvelistv5 – Published: 2026-06-23 17:18 – Updated: 2026-06-26 18:56

Title

Deno Node TCPWrap numeric hostname aliases bypass --deny-net resolved-IP deny checks

Summary

Deno is a JavaScript, TypeScript, and WebAssembly runtime. Prior to 2.8.0, the Node.js compatibility TCP path checked the permission against the original hostname string before resolution and then did not re-check after resolution. A caller could therefore pass a numeric alias of an IP address (for example the decimal integer 2130706433 or the hex form 0x7f000001, both of which resolve to 127.0.0.1) and reach the denied destination through node:net.connect or node:http.request's { host, port } options form. This vulnerability is fixed in 2.8.0.

Severity

6.5 (Medium)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-26 18:55 UTC

CWE

CWE-284 - Improper Access Control

Assigner

GitHub_M mitre root

References

1 reference

URL	Tags
https://github.com/denoland/deno/security/advisor…	x_refsource_CONFIRM

Impacted products

1 product

Vendor	Product	Version	CPE status
denoland	deno	Affected: < 2.8.0	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-49411

Vulnerability from fkie_nvd - Published: 2026-06-23 18:18 - Updated: 2026-06-26 20:17

Severity

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

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/denoland/deno/security/advisories/GHSA-v8fw-85r8-5m23	Exploit, Mitigation, Third Party Advisory
	134c704f-9b21-4f2e-91b3-4a467353bcc0	https://github.com/denoland/deno/security/advisories/GHSA-v8fw-85r8-5m23	Exploit, Mitigation, Third Party Advisory

Impacted products

	Vendor	Product	Version
	deno	deno	*

JSON

To clipboard

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GHSA-V8FW-85R8-5M23

Vulnerability from github – Published: 2026-06-16 19:09 – Updated: 2026-07-20 21:01

Summary

Deno: Node TCPWrap numeric hostname aliases bypass --deny-net resolved-IP deny checks

Details

Summary

Deno's network permission model is designed so that --deny-net rules apply to the resolved IP address of a destination, not just the literal string supplied by the caller. That means --deny-net=127.0.0.1 (or --deny-net=127.0.0.0/8) is expected to block any attempt to reach loopback, regardless of how the hostname is spelled.

On affected versions, the Node.js compatibility TCP path checked the permission against the original hostname string before resolution and then did not re-check after resolution. A caller could therefore pass a numeric alias of an IP address (for example the decimal integer 2130706433 or the hex form 0x7f000001, both of which resolve to 127.0.0.1) and reach the denied destination through node:net.connect or node:http.request's { host, port } options form.

The native Deno.connect(), fetch(), and URL-string variants of node:http.request("http://...") were not affected, because they either re-checked permissions after resolution or normalized the hostname through the URL parser before checking.

Proof of concept

Run on Deno 2.7.14, with a local TCP listener on 127.0.0.1:<PORT>:

import net from "node:net";

// --allow-net + --deny-net=127.0.0.0/8
// (or even --deny-net=127.0.0.1:<PORT>)
net.connect({ host: "2130706433", port: PORT });     // CONNECTED ❌
net.connect({ host: "0x7f000001", port: PORT });     // CONNECTED ❌
net.connect({ host: "127.0.0.1",  port: PORT });     // denied ✅

The same primitive reached the loopback HTTP listener through node:http when the destination was passed as options rather than as a URL string:

import http from "node:http";

// options-form host — bypasses the deny rule on affected versions
http.request({ hostname: "2130706433", port: PORT, path: "/" }).end();

// URL-string form — correctly denied (URL parser normalizes the host)
http.request(`http://2130706433:${PORT}/`).end();

The server-side log showed the bypassed requests arriving from 127.0.0.1 with the numeric alias preserved in the Host header.

Impact

A program that intentionally allows broad outbound network access but uses --deny-net to carve out protected destinations, typically loopback, private/internal ranges, or cloud-instance metadata IPs, could be made to reach those denied destinations from less-trusted code (a dependency, plugin, or attacker-controlled input) that funnels through node:net.connect({ host }) or node:http.request({ hostname }).

The CVSS vector reflects this as a local-attack-vector, permissions-required confidentiality impact: the attacker needs to be able to run code inside the Deno process, and the demonstrated primitive is "reach an explicitly denied IP." It does not by itself exfiltrate data or execute code; the further impact depends on what the now-reachable endpoint exposes.

The confirmed scope is IPv4 numeric hostname aliases reaching a denied resolved IP through the Node TCPWrap / options-host path. URL strings, node:http2, undici, and IPv6 numeric/mapped-address variants were not exhaustively tested by the reporter.

Not affected

Programs that do not use --deny-net at all (the bug is specifically about deny rules being bypassed; allow rules were always checked against the original string).
Native Deno networking APIs (Deno.connect, Deno.connectTls, fetch, ...), these already re-checked permissions after resolution as of PR #33203.
URL-string callers such as fetch("http://2130706433/") or node:http.request("http://2130706433/"), the URL parser normalized the hostname to its dotted-quad form before the permission check ran.
Calls that do not provide host/hostname (e.g. connecting by IP literal or by a name that the deny rule already matches verbatim).

Workarounds

If you cannot upgrade immediately, reduce exposure by:

Preferring an --allow-net allowlist over a --deny-net denylist. An allowlist denies numeric aliases by default because they don't match the listed hostnames; only the destinations you've explicitly permitted can be reached.
Validating untrusted host input before passing it to node:net.connect / node:http.request. Reject hostnames that are purely decimal integers (/^\d+$/) or begin with 0x, as these are the alias forms exploited by the bypass.
Avoiding the Node options-host path for sensitive calls in favour of URL-string forms, which are normalized by the URL parser before the permission check.

Severity

6.5 (Medium)


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

Show details on source website

JSON

To clipboard

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    "github_reviewed": true,
    "github_reviewed_at": "2026-06-16T19:09:46Z",
    "nvd_published_at": "2026-06-23T18:18:03Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nDeno\u0027s network permission model is designed so that `--deny-net` rules apply to the **resolved IP address** of a destination, not just the literal string supplied by the caller. That means `--deny-net=127.0.0.1` (or `--deny-net=127.0.0.0/8`) is expected to block any attempt to reach loopback, regardless of how the hostname is spelled.\n\nOn affected versions, the Node.js compatibility TCP path checked the permission against the **original hostname string** before resolution and then did not re-check after resolution. A caller could therefore pass a numeric alias of an IP address (for example the decimal integer `2130706433` or the hex form `0x7f000001`, both of which resolve to `127.0.0.1`) and reach the denied destination through `node:net.connect` or `node:http.request`\u0027s `{ host, port }` options form.\n\nThe native `Deno.connect()`, `fetch()`, and URL-string variants of `node:http.request(\"http://...\")` were not affected, because they either re-checked permissions after resolution or normalized the hostname through the URL parser before checking.\n\n## Proof of concept\n\nRun on Deno `2.7.14`, with a local TCP listener on `127.0.0.1:\u003cPORT\u003e`:\n\n```js\nimport net from \"node:net\";\n\n// --allow-net + --deny-net=127.0.0.0/8\n// (or even --deny-net=127.0.0.1:\u003cPORT\u003e)\nnet.connect({ host: \"2130706433\", port: PORT });     // CONNECTED \u274c\nnet.connect({ host: \"0x7f000001\", port: PORT });     // CONNECTED \u274c\nnet.connect({ host: \"127.0.0.1\",  port: PORT });     // denied \u2705\n```\n\nThe same primitive reached the loopback HTTP listener through `node:http` when the destination was passed as options rather than as a URL string:\n\n```js\nimport http from \"node:http\";\n\n// options-form host \u2014 bypasses the deny rule on affected versions\nhttp.request({ hostname: \"2130706433\", port: PORT, path: \"/\" }).end();\n\n// URL-string form \u2014 correctly denied (URL parser normalizes the host)\nhttp.request(`http://2130706433:${PORT}/`).end();\n```\n\nThe server-side log showed the bypassed requests arriving from `127.0.0.1` with the numeric alias preserved in the `Host` header.\n\n## Impact\n\nA program that intentionally allows broad outbound network access but uses `--deny-net` to carve out protected destinations, typically loopback, private/internal ranges, or cloud-instance metadata IPs, could be made to reach those denied destinations from less-trusted code (a dependency, plugin, or attacker-controlled input) that funnels through `node:net.connect({ host })` or `node:http.request({ hostname })`.\n\nThe CVSS vector reflects this as a local-attack-vector, permissions-required confidentiality impact: the attacker needs to be able to run code inside the Deno process, and the demonstrated primitive is \"reach an explicitly denied IP.\" It does not by itself exfiltrate data or execute code; the further impact depends on what the now-reachable endpoint exposes.\n\nThe confirmed scope is **IPv4 numeric hostname aliases** reaching a denied resolved IP through the Node TCPWrap / options-host path. URL strings, `node:http2`, `undici`, and IPv6 numeric/mapped-address variants were not exhaustively tested by the reporter.\n\n## Not affected\n\n- Programs that do not use `--deny-net` at all (the bug is specifically about deny rules being bypassed; allow rules were always checked against the original string).\n- Native Deno networking APIs (`Deno.connect`, `Deno.connectTls`, `fetch`, ...), these already re-checked permissions after resolution as of PR #33203.\n- URL-string callers such as `fetch(\"http://2130706433/\")` or `node:http.request(\"http://2130706433/\")`, the URL parser normalized the hostname to its dotted-quad form before the   permission check ran.\n- Calls that do not provide `host`/`hostname` (e.g. connecting by IP literal or by a name that the deny rule already matches verbatim).\n\n## Workarounds\n\nIf you cannot upgrade immediately, reduce exposure by:\n\n- **Preferring an `--allow-net` allowlist over a `--deny-net` denylist.** An allowlist denies numeric aliases by default because they don\u0027t match the listed hostnames; only the destinations you\u0027ve explicitly permitted can be reached.\n- **Validating untrusted host input** before passing it to `node:net.connect` / `node:http.request`. Reject hostnames that are purely decimal integers (`/^\\d+$/`) or begin with `0x`, as these are the alias forms exploited by the bypass.\n- **Avoiding the Node options-host path for sensitive calls** in favour of URL-string forms, which are normalized by the URL parser before the permission check.",
  "id": "GHSA-v8fw-85r8-5m23",
  "modified": "2026-07-20T21:01:40Z",
  "published": "2026-06-16T19:09:46Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/denoland/deno/security/advisories/GHSA-v8fw-85r8-5m23"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-49411"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/denoland/deno"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Deno: Node TCPWrap numeric hostname aliases bypass --deny-net resolved-IP deny checks"
}

Sightings

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Detection rules are retrieved from Rulezet.

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Action not permitted

CVE-2026-49411 (GCVE-0-2026-49411)

FKIE_CVE-2026-49411

GHSA-V8FW-85R8-5M23

Summary

Proof of concept

Impact

Not affected

Workarounds

Tags

Sightings

Nomenclature

Related by attack behaviour