# CVE-2019-3902: Mercurial Path Traversal/Link Following vulnerability

Source: https://junglewise.ai/threats/cve-2019-3902-mercurial-path-traversal-link-following-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2019-04-22  
License: CC BY 4.0 with a link back

CVE-2019-3902 · Severity: low · CVSS 3 · Published 2019-04-22

A flaw was found in Mercurial before 4.9. It was possible to use symlinks and subrepositories to defeat Mercurial's path-checking logic and write files outside a repository.

Technologies: [mercurial (PyPI)](https://junglewise.ai/threats/technologies/mercurial). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2019-3902 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2019-3902 being exploited in the wild.

**How severe is CVE-2019-3902?** Low severity, with a CVSS score of 3, published 22 April 2019.

**Which products and versions are affected?** mercurial (PyPI) ECOSYSTEM:introduced=0,fixed=4.9.

**Is there a fix for CVE-2019-3902?** Yes. mercurial (PyPI): upgrade to 4.9 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2019-3902?** Check whether you run mercurial (PyPI) 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

- mercurial (PyPI): upgrade to 4.9 or later

  ```sh
  pip install "mercurial>=4.9"
  ```


## Affected products

- mercurial (PyPI) ECOSYSTEM:introduced=0,fixed=4.9

## Identifiers

- CVE-2019-3902
- GHSA-mq66-vcfc-8246
- PYSEC-2019-188

## Related threats

- [PYSEC-2026-666 - Mercurial Directory traversal vulnerability](https://junglewise.ai/threats/cve-2008-2942-mercurial-directory-traversal-vulnerability)
- [PYSEC-2026-665 - Mercurial Improper Certificate Validation vulnerability](https://junglewise.ai/threats/cve-2010-4237-mercurial-improper-certificate-validation-vulnerability)
- [JGit Improper Input Validation vulnerability](https://junglewise.ai/threats/cve-2014-9390-jgit-improper-input-validation-vulnerability)
- [PYSEC-2018-91 - cext/manifest.c in Mercurial before 4.7.2 has an out-of-bounds read during parsing of a malformed manifest entry.](https://junglewise.ai/threats/cve-2018-17983-mercurial-out-of-bounds-read-vulnerability)
- [Mercurial Improper Input Validation vulnerability](https://junglewise.ai/threats/cve-2018-13346-mercurial-improper-input-validation-vulnerability)