# CVE-2026-76845: adm-zip symlink following in archive extraction

Source: https://junglewise.ai/threats/cve-2026-76845-adm-zip-symlink-following-in-archive-extraction  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-24. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-76845 · Severity: medium · CVSS 6.5 · Published 2026-08-24

adm-zip is a popular Node.js library for creating and extracting ZIP archives. The library fails to properly handle symbolic links during extraction, allowing an attacker who can pre-create a symlink in the extraction directory to write arbitrary files outside the intended extraction folder. This could enable an attacker to overwrite critical application files, inject malicious code, or manipulate system configurations in environments where shared or predictable extraction directories are used (such as temporary folders or CI/CD workspaces).

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

## Quick answers

**Is CVE-2026-76845 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-76845 being exploited in the wild.

**How severe is CVE-2026-76845?** Medium severity, with a CVSS score of 6.5, published 24 August 2026.

**Which products and versions are affected?** adm-zip (npm) >= 0.5.9, <= 0.6.0, SEMVER:introduced=0.5.9,last_affected=0.6.0.

**Is there a fix for CVE-2026-76845?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-76845 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-76845?** Check whether you run adm-zip (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.

## Technical details

The vulnerability is a link-following flaw (CWE-59) in adm-zip's extraction functions. The Utils.sanitize function in util/utils.js performs path traversal checks only on the string representation of archive entry names, comparing against the resolved extraction root. However, Utils.writeFileTo uses fs.openSync(path, "w", 0o666) to open files for writing, which resolves symlinks and contains no O_NOFOLLOW flag or pre-write fs.lstatSync check. When an extraction path component is a symlink pointing outside the extraction root, the library follows that symlink and writes attacker-controlled content to the target file, then changes its permissions. The extraction functions affected are extractAllTo, extractAllToAsync, and extractEntryTo. Exploitation requires: (1) the attacker can create a symlink in the extraction directory (e.g., in /tmp or a CI workspace), (2) the extraction process has overwrite mode enabled (because fs.existsSync also resolves symlinks and would otherwise decline), and (3) the attacker has write permissions to the extraction directory. No patch version is currently available according to the advisory.

## Affected products

- cthackers adm-zip 0.5.9 through 0.6.0

## Identifiers

- CVE-2026-76845
- GHSA-vwc7-r8mq-g2x9

## Timeline

- 2026-08-24: disclosed
- 2026-08-24: advisory: GitHub Advisory Database and NVD published
- 2026-09-08: other: GitHub advisory reviewed and updated

## References

- [https://github.com/cthackers/adm-zip](https://github.com/cthackers/adm-zip)
- [https://github.com/cthackers/adm-zip/blob/v0.6.0/util/utils.js](https://github.com/cthackers/adm-zip/blob/v0.6.0/util/utils.js)
- [https://www.vulncheck.com/advisories/adm-zip-through-arbitrary-file-overwrite-via-symlink-following-on-extraction](https://www.vulncheck.com/advisories/adm-zip-through-arbitrary-file-overwrite-via-symlink-following-on-extraction)
- [https://github.com/cthackers/adm-zip/issues/574](https://github.com/cthackers/adm-zip/issues/574)
- [https://github.com/cthackers/adm-zip/pull/575](https://github.com/cthackers/adm-zip/pull/575)

## Related threats

- [Adm-zip incorrect permission assignment with keepOriginalPermission](https://junglewise.ai/threats/cve-2026-114105-adm-zip-before-0-6-1-contains-an-incorrect-permission-assignment)
- [adm-zip permission bit extraction privilege escalation](https://junglewise.ai/threats/cve-2026-102282-adm-zip-extraction-preserves-suid-sgid-bits-from-untrusted-zips)
- [adm-zip duplicate ZIP entry name validation bypass](https://junglewise.ai/threats/adm-zip-duplicate-zip-entry-names-getentry-and-extractallto-resolve-to-42f08f8e)
- [adm-zip getDataAsync() decompression bomb bypass](https://junglewise.ai/threats/adm-zip-getdataasync-bypasses-the-maxoutputlength-size-guard-enforced-3e032cd1)
- [adm-zip async decompression denial of service](https://junglewise.ai/threats/adm-zip-unhandled-error-event-in-async-deflate-decompression-crashes-337da7e4)