# CVE-2026-59871: isaacs node-tar denial of service via PAX numeric path type confusion

Source: https://junglewise.ai/threats/cve-2026-59871-isaacs-node-tar-denial-of-service-via-pax-numeric-path-type  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-08. Updated: 2026-07-20  
License: CC BY 4.0 with a link back

CVE-2026-59871 · Severity: medium · CVSS 5.3 · Published 2026-07-08

A vulnerability in the node-tar library, a popular tool for handling compressed archives in Node.js, allows a small, specially crafted file to crash any application that attempts to extract it. This can lead to a complete service outage for tools like npm, CI/CD pipelines, and file upload services. The crash is difficult to prevent because it bypasses standard error-handling mechanisms.

Technologies: [tar (npm)](https://junglewise.ai/threats/technologies/npm-tar). Vendors: [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2026-59871 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-59871 being exploited in the wild.

**How severe is CVE-2026-59871?** Medium severity, with a CVSS score of 5.3, published 8 July 2026.

**Which products and versions are affected?** tar (npm) SEMVER:introduced=0,fixed=7.5.18.

**Is there a fix for CVE-2026-59871?** Yes. tar (npm): upgrade to 7.5.18 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-59871 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-59871?** Check whether you run tar (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- tar (npm): upgrade to 7.5.18 or later

  ```sh
  npm install tar@7.5.18
  ```


## Technical details

The vulnerability is an incorrect type conversion (CWE-704) in the PAX header parser within `pax.ts`. The `parseKV` function uses a regular expression `/^[0-9]+$/` to identify numeric values and coerces them to JavaScript numbers using the unary plus operator. When a PAX header contains an all-digit `path` or `linkpath`, the resulting numeric value is passed to `Unpack.CHECKPATH`, which calls `.split('/')`. Because numbers do not possess the `.split` method, a synchronous `TypeError` is thrown. This error propagates as an `uncaughtException`, bypassing standard `'error'` or `'warn'` event handlers and the `strict: false` configuration. The issue is patched in version 7.5.18.

## Affected products

- isaacs (node-tar) tar <= 7.5.17

## Identifiers

- CVE-2026-59871
- GHSA-w8wr-v893-vjvp

## Timeline

- 2026-06-27: disclosed
- 2026-06-27: patched: Fixed in version 7.5.18
- 2026-07-20: advisory

## References

- [https://api.github.com/users/homanp](https://api.github.com/users/homanp)
- [https://github.com/homanp](https://github.com/homanp)
- [https://api.github.com/users/homanp/gists%7B/gist_id%7D](https://api.github.com/users/homanp/gists%7B/gist_id%7D)
- [https://api.github.com/users/homanp/repos](https://api.github.com/users/homanp/repos)
- [https://avatars.githubusercontent.com/u/2464556?v=4](https://avatars.githubusercontent.com/u/2464556?v=4)
- [https://api.github.com/users/homanp/events%7B/privacy%7D](https://api.github.com/users/homanp/events%7B/privacy%7D)

## Related threats

- [npm tar stack overflow in mapHas filter with long paths](https://junglewise.ai/threats/cve-2026-73566-npm-tar-stack-overflow-in-maphas-filter-with-long-paths)
- [node-tar denial of service via NUL byte in PAX records](https://junglewise.ai/threats/cve-2026-59875-node-tar-denial-of-service-via-nul-byte-in-pax-records)
- [isaacs node-tar infinite loop in tar.replace](https://junglewise.ai/threats/cve-2026-59874-isaacs-node-tar-infinite-loop-in-tar-replace)
- [isaacs node-tar Denial of Service via Gzip Bomb](https://junglewise.ai/threats/cve-2026-59873-isaacs-node-tar-denial-of-service-via-gzip-bomb)
- [isaacs node-tar interpretation conflict in PAX header parsing](https://junglewise.ai/threats/cve-2026-53655-isaacs-node-tar-interpretation-conflict-in-pax-header-parsing)