# CVE-2019-18197: Nokogiri Use After Free in libxslt dependency

Source: https://junglewise.ai/threats/cve-2019-18197-nokogiri-use-after-free-in-libxslt-dependency  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2022-05-24. Updated: 2026-06-09  
License: CC BY 4.0 with a link back

CVE-2019-18197 · Severity: high · CVSS 7.5 · Published 2022-05-24

Nokogiri, a popular Ruby library used for parsing and manipulating XML and HTML documents, was found to be using a vulnerable version of the libxslt library. This flaw could allow an attacker to cause a service crash, disclose sensitive information from memory, or potentially execute unauthorized code when the application processes a specially crafted document. Organizations using Nokogiri should update to version 1.10.5 or later to ensure they are using a patched version of the underlying processing engine.

Technologies: [nokogiri (RubyGems)](https://junglewise.ai/threats/technologies/nokogiri). Vendors: [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2019-18197 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2019-18197 being exploited in the wild.

**How severe is CVE-2019-18197?** High severity, with a CVSS score of 7.5, published 24 May 2022.

**Which products and versions are affected?** nokogiri (RubyGems) < 1.10.5, ECOSYSTEM:introduced=0,fixed=1.10.5.

**Is there a fix for CVE-2019-18197?** Yes. nokogiri (RubyGems): upgrade to 1.10.5 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2019-18197 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2019-18197?** Check whether you run nokogiri (RubyGems) 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

- nokogiri (RubyGems): upgrade to 1.10.5 or later

  ```sh
  bundle update nokogiri
  ```


## Technical details

Nokogiri versions prior to 1.10.5 bundle libxslt 1.1.33, which contains a vulnerability in the `xsltCopyText` function within `transform.c`. The issue stems from a pointer variable not being properly reset under specific conditions, leading to a use-after-free or use of an uninitialized resource (CWE-416, CWE-908). An attacker can exploit this by providing a malicious XSLT stylesheet or XML document that triggers specific memory reuse patterns. Successful exploitation can result in a failed bounds check, allowing for out-of-bounds writes or the disclosure of uninitialized memory contents. The vulnerability is addressed in Nokogiri 1.10.5 by upgrading the bundled libxslt to version 1.1.34.

## Affected products

- Nokogiri Nokogiri < 1.10.5

## Identifiers

- CVE-2019-18197
- GHSA-242x-7cm6-4w8j

## Timeline

- 2019-10-18: disclosed: NVD publication date
- 2022-05-24: advisory: GitHub Advisory published

## References

- [https://access.redhat.com/errata/RHSA-2020:0514](https://access.redhat.com/errata/RHSA-2020:0514)
- [https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15746](https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15746)
- [https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15768](https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15768)
- [https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15914](https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=15914)
- [https://gitlab.gnome.org/GNOME/libxslt/commit/2232473733b7313d67de8836ea3b29eec6e8e285](https://gitlab.gnome.org/GNOME/libxslt/commit/2232473733b7313d67de8836ea3b29eec6e8e285)

## Related threats

- [Nokogiri use-after-free in attribute replacement](https://junglewise.ai/threats/cve-2026-126064-nokogiri-is-an-open-source-xml-and-html-library-for-the-ruby)
- [Nokogiri HTML5 serializer mutation XSS via noscript and attributes](https://junglewise.ai/threats/cve-2026-126063-nokogiri-is-an-open-source-xml-and-html-library-for-the-ruby)
- [JRuby: NONET is bypassed for external DTDs and entities when the systemId uses a short-form IPv4 host](https://junglewise.ai/threats/cve-2026-126062-nokogiri-is-an-open-source-xml-and-html-library-for-the-ruby)
- [Nokogiri unchecked return value in canonicalize method](https://junglewise.ai/threats/nokogiri-unchecked-return-value-in-canonicalize-method-3863de91)
- [Nokogiri XSLT transform memory leak](https://junglewise.ai/threats/nokogiri-xslt-transform-memory-leak-0441ddf7)