CVE-2026-69198: ip-address A CIDR Suffix On The Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4xrf-jv44-h6hh",
  "modified" : "2026-08-03T19:59:33Z",
  "published" : "2026-08-03T19:59:33Z",
  "aliases" : [ "CVE-2026-69198" ],
  "summary" : "ip-address: a CIDR suffix on the parsed address suppresses special-use classification and can bypass SSRF and trust-boundary checks",
  "details" : "### Summary\n\nEvery special-use classification method is built on `isInSubnet`, which short-circuits to `false` whenever the address's own subnet mask is *shorter* than the reference range's mask. That mask comes verbatim from the CIDR suffix on the parsed input, so appending a suffix such as `/0` suppresses classification entirely: `isLoopback()`, `isPrivate()`, `isLinkLocal()`, `isCGNAT()`, `isMulticast()`, `isUnspecified()`, `isBroadcast()`, `isULA()`, and `getType()` all report an internal address as unremarkable, while `correctForm()` and `address` still return the real internal target.\n\nAn application that builds a network trust-boundary decision on these checks (for example a filter intended to block Server-Side Request Forgery, or SSRF) may therefore treat an internal target as external and allow the request. SSRF is an attack in which a user-supplied address coaxes the server into making a request to an internal destination the user could not otherwise reach, such as a loopback service or a cloud metadata endpoint.\n\n### Details\n\n`isInSubnet` in `src/common.ts` opens with a guard that compares the two prefix lengths:\n\n```js\nexport function isInSubnet(this, address) {\n  if (this.subnetMask < address.subnetMask) {\n    return false;                                  // <-- reached before any bit comparison\n  }\n\n  if (this.mask(address.subnetMask) === address.mask()) {\n    return true;\n  }\n\n  return false;\n}\n```\n\nThat guard is correct for the question `isInSubnet` is named for — whether one *network* is contained in another, where a `/0` network genuinely is not inside a `/8`. It is wrong for classification, which asks a question about the address itself and must not depend on the prefix the caller happened to write. `/0` is shorter than every reference prefix in the special-use tables (loopback `/8`, link-local `/16`, CGNAT `/10`, ULA `/7`, multicast `/4`), so for a classification call the bit comparison is never reached and the method returns `false`.\n\nThe underlying bit comparison is correct, and `mask(n)` already returns the first `n` bits of the full parsed address independently of `subnetMask` — the defect is solely that the containment guard sits in the classification path. Host bits are retained through parsing, so `correctForm()` still yields the real target and the address remains fully usable for connecting.\n\n`/0` is the universal case because it is shorter than every reference prefix, but any suffix shorter than the specific range being tested has the same effect: `10.0.0.5/7` defeats `isPrivate()` for `10.0.0.0/8`.\n\n### Affected versions\n\n`>= 10.1.1, <= 10.2.1`. The `is*` classification API was introduced for `Address4` in 10.1.1 and extended to `Address6` in 10.2.0; releases before 10.1.1 do not expose it and are not affected through this vector. The containment guard itself is much older, but `isInSubnet` alone is a subnet-containment predicate whose behavior here is correct.\n\nThis also defeats the fix released in 10.2.1 for GHSA-22jq-vg5j-6vgg: that release classifies IPv4-mapped and NAT64 addresses by their embedded IPv4 address, but the normalization is reached through `isInSubnet`, so `::ffff:127.0.0.1/0` reverts to being reported as non-internal.\n\n### Impact\n\nEvery classifier is affected on both `Address4` and `Address6`. The sole exception is `Address6.isLinkLocal()` for *native* `fe80::/10` addresses, which compares raw bits directly; its IPv4-mapped path is still affected.\n\n| Address | Reported as | Actually points at |\n|---|---|---|\n| `127.0.0.1/0` | not loopback | loopback (`127.0.0.0/8`) |\n| `10.0.0.1/0`, `10.0.0.5/7` | not private | RFC 1918 `10/8` |\n| `172.16.5.5/0` | not private | RFC 1918 `172.16/12` |\n| `192.168.1.1/0` | not private | RFC 1918 `192.168/16` |\n| `169.254.169.254/0` | not link-local | link-local / cloud metadata (IMDS) |\n| `100.64.0.1/0` | not CGNAT | CGNAT `100.64/10` |\n| `0.0.0.0/0`, `255.255.255.255/0` | not unspecified / not broadcast | unspecified / broadcast |\n| `::1/0` | not loopback | IPv6 loopback |\n| `fc00::1/0` | not ULA, not private | IPv6 ULA `fc00::/7` |\n| `ff02::1/0` | not multicast | IPv6 multicast |\n| `::ffff:127.0.0.1/0` | not loopback | loopback, via IPv4-mapped |\n| `::ffff:169.254.169.254/0` | not link-local | IMDS, via IPv4-mapped |\n| `64:ff9b::7f00:1/0` | not loopback | loopback, via NAT64 |\n\n`getType()` returns `Global unicast` for all of the IPv6 cases above, and `getScope()` follows it.\n\n### Reachability\n\nA CIDR suffix is not legal in a URL host, so this is not reachable through the most common SSRF shape. `new URL('http://127.0.0.1/0')` parses `hostname` as `127.0.0.1` and `pathname` as `/0`, and a guard that classifies the extracted hostname is unaffected. Exploitation requires an application that accepts a bare address string that may carry a suffix and passes it to the constructor before classifying — for example an allow/deny field, a webhook target, or a proxy destination taken as a plain host rather than parsed out of a URL.\n\n### Proof of concept\n\n`npm i ip-address@10.2.1`, then:\n\n```js\nconst { Address4, Address6 } = require('ip-address');\n\n// true => block as internal, false => allow outbound\nfunction isBlocked(host) {\n  try {\n    const a = new Address4(host);\n    return a.isPrivate() || a.isLoopback() || a.isLinkLocal() || a.isCGNAT()\n        || a.isMulticast() || a.isUnspecified() || a.isBroadcast();\n  } catch {}\n  try {\n    const a = new Address6(host);\n    return a.isPrivate() || a.isLoopback() || a.isLinkLocal() || a.isULA()\n        || a.isMulticast() || a.isUnspecified();\n  } catch {}\n  return false;\n}\n\nfor (const h of ['127.0.0.1', '10.0.0.1', '::1',\n                 '127.0.0.1/0', '10.0.0.5/7', '169.254.169.254/0',\n                 '::1/0', '::ffff:127.0.0.1/0', '64:ff9b::7f00:1/0']) {\n  console.log(isBlocked(h) ? 'BLOCK ' : 'ALLOW ', h, '->', new (h.includes(':') ? Address6 : Address4)(h).correctForm());\n}\n```\n\nOn affected versions every suffixed internal target is allowed, and `correctForm()` shows the request would reach the real internal address:\n\n```\nBLOCK  127.0.0.1 -> 127.0.0.1\nBLOCK  10.0.0.1 -> 10.0.0.1\nBLOCK  ::1 -> ::1\nALLOW  127.0.0.1/0 -> 127.0.0.1\nALLOW  10.0.0.5/7 -> 10.0.0.5\nALLOW  169.254.169.254/0 -> 169.254.169.254\nALLOW  ::1/0 -> ::1\nALLOW  ::ffff:127.0.0.1/0 -> ::ffff:7f00:1\nALLOW  64:ff9b::7f00:1/0 -> 64:ff9b::7f00:1\n```\n\nThe first three lines are blocked as expected; the same destinations with a CIDR suffix are allowed through.\n\n### Remediation\n\nUpgrade to the patched release. In the fix, classification no longer consults the address's own prefix: a new `isHostInSubnet()` compares the address's host bits against the reference range only, and every classifier (`isLoopback`, `isPrivate`, `isLinkLocal`, `isCGNAT`, `isMulticast`, `isUnspecified`, `isBroadcast`, `isULA`, `isMapped4`, `isTeredo`, `is6to4`, `isDocumentation`, `getType`, and the IPv4-mapped/NAT64 normalization behind `embeddedIPv4`) uses it. `isInSubnet` keeps its subnet-containment semantics unchanged, including the guard that a wider network is not contained in a narrower one. After upgrading, `new Address4('127.0.0.1/0').isLoopback()` returns `true`.\n\nIf you cannot upgrade immediately, strip the suffix before classifying by re-parsing `addressMinusSuffix`:\n\n```js\nconst parsed = new Address4(userInput);\nconst host = new Address4(parsed.addressMinusSuffix);   // classify this one\n```\n\n### A note on SSRF defense\n\nThese methods are address classifiers, not a complete SSRF defense. Regardless of this fix, a robust SSRF guard must resolve the hostname and validate the *resolved* IP against the socket it connects to, and account for DNS rebinding and redirects. Treat these checks as one layer, not the only one.\n\n### Credit\n\nReported by @hi-im-glitchless.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:H/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "ip-address"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "10.1.1"
      }, {
        "fixed" : "10.2.2"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 10.2.1"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/beaugunderson/ip-address/security/advisories/GHSA-4xrf-jv44-h6hh"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/beaugunderson/ip-address/commit/488fe9bc7c35363b4b090494fc38c266d217740d"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/beaugunderson/ip-address"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/beaugunderson/ip-address/releases/tag/v10.2.2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-20", "CWE-918" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-08-03T19:59:33Z",
    "nvd_published_at" : null
  }
}