CVE-2021-3537 Nokogiri Implements libxml2 version vulnerable to null pointer dereferencing

What is CVE-2021-3537?

CVE-2021-3537 is a medium-severity vulnerability in Debian Debian Linux, published on 14 May 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

A vulnerability found in libxml2 in versions before 2.9.11 shows that it did not propagate errors while parsing XML mixed content, causing a NULL dereference. If an untrusted XML document was parsed in recovery mode and post-validated, the flaw could be used to crash the application. The highest threat from this vulnerability is to system availability.

Weakness: CWE-476

Which versions are affected by CVE-2021-3537?

2 open source packages ship an affected version, including nokogiri. It affects 19 products.

Products include Debian Debian Linux, Fedoraproject Fedora, Netapp Active Iq Unified Manager, Netapp Clustered Data Ontap, Netapp Clustered Data Ontap Antivirus Connector, Netapp Hci H410c Firmware and 13 more.

How do I fix CVE-2021-3537?

Upgrade nokogiri to 1.11.4 or later.

Is CVE-2021-3537 being exploited?

There is no known exploitation of CVE-2021-3537 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2021-3537, DEBIAN-CVE-2021-3537, ECHO-ba64-c94d-5407, GHSA-286v-pcf5-25rc, JLSEC-2025-70, UBUNTU-CVE-2021-3537.