How severe is CVE-2019-18197?

CVE-2019-18197 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2019-18197?

CVE-2019-18197 affects the following packages: nokogiri (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2019-18197?

Update nokogiri to 1.10.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-18197 is resolved across your whole dependency graph.

How do I detect CVE-2019-18197 in my RubyGems dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nokogiri, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2019-18197 if there is no patch (or I can't update yet)?

Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Is CVE-2019-18197 actively exploited in the wild?

No public exploit code has been indexed for CVE-2019-18197 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2019-18197?

CVE-2019-18197 has an EPSS (Exploit Prediction Scoring System) score of 4.4%, placing it in the 91th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2019-18197?

CVE-2019-18197 is classified as Use After Free (CWE-416), CWE-908 (CWE-908). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2019-18197 published, and has it been updated?

CVE-2019-18197 was published on October 18, 2019 and was last updated on April 16, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

HIGH severity

CVE-2019-18197 — nokogiri

HIGH

CVE-2019-18197 is a high-severity (CVSS 7.5) Use After Free vulnerability in nokogiri. A fix is available for nokogiri — see the affected versions and patch details below.

Nokogiri affected by libxslt Use of Uninitialized Resource/Use After Free vulnerability

Also known asGHSA-242x-7cm6-4w8j

Published

Oct 18, 2019

Updated

Apr 16, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2019-18197.

EPSS Exploitation Probability

via FIRST.org ↗

4.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs91th percentile — riskier than 91% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

💎nokogiri

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.

Description

Nokogiri prior to version 1.10.5 contains a vulnerable version of libxslt. Nokogiri version 1.10.5 upgrades the dependency to libxslt 1.1.34, which contains a patch for this issue.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`nokogiri`	all versions	1.10.5`bundle update nokogiri --conservative`

Affected Products

3 products · 8 configurations

ubuntu linuxcanonical

6 versions

12.0414.0416.0418.0419.0419.10

debian linuxdebian

1 version

8.0

Application

libxsltxmlsoft

1 version

1.1.33

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nokogiri, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nokogiri to 1.10.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2019-18197 is resolved across your whole dependency graph.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Red Hat OpenStack consumes fixes from the base Red Hat Enterprise Linux Operating System. Therefore the libxslt package provided by Red Hat OpenStack has been marked as 'will not fix'.

Product	Fixed in	Advisory
Red Hat Enterprise Linux 6 Supplementary	`chromium-browser-0:80.0.3987.87-1.el6_10`	RHSA-2020:0514
Red Hat Enterprise Linux 7	`libxslt-0:1.1.28-6.el7`	RHSA-2020:4005
Red Hat Enterprise Linux 8	`libxslt-0:1.1.32-5.el8`	RHSA-2020:4464

UbuntuHIGH

USN-4164-1Ubuntu

Frequently Asked Questions

In xsltCopyText in transform.c in libxslt 1.1.33, a pointer variable isn't reset under certain circumstances. If the relevant memory area happened to be freed and reused in a certain way, a bounds check could fail and memory outside a buffer could be written to, or uninitialized data could be disclosed. Nokogiri prior to version 1.10.5 contains a vulnerable version of libxslt. Nokogiri version 1.10.5 upgrades the dependency to libxslt 1.1.34, which contains a patch for this issue.

O3 Security · Impact-Aware SCA

Is CVE-2019-18197 in your dependencies?

Find it across RubyGems, including transitive dependencies.

Scan my dependencies How O3 SCA works