CVE-2026-57434 in nokogiri
Summary
by MITRE • 06/25/2026
Nokogiri is an open source XML and HTML library for the Ruby programming language. Prior to 1.19.4, Nokogiri contains a bug when calling certain methods on allocated-but-uninitialized native wrapper classes that inherit from Nokogiri::XML::Node. This caused a NULL pointer dereference that could crash the process. This vulnerability is fixed in 1.19.4.
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Analysis
by VulDB Data Team • 06/25/2026
The Nokogiri library represents a critical security vulnerability affecting Ruby applications that process XML and HTML content through native wrapper classes inheriting from Nokogiri::XML::Node. This flaw manifests when specific methods are invoked on objects that have been allocated but remain uninitialized, creating a dangerous condition where memory references become invalid and lead to system instability.
The technical root cause of this vulnerability lies in improper handling of object initialization states within the native C extensions that power Nokogiri's functionality. When methods are called against these uninitialized wrapper objects, the underlying memory management system attempts to dereference null pointers that should have been properly initialized during object construction. This NULL pointer dereference represents a classic software defect pattern that aligns with CWE-476, which specifically addresses NULL pointer dereferences in software implementations. The vulnerability exists at the intersection of Ruby's object model and native C code execution, where the boundary between managed and unmanaged memory creates opportunities for crashes when initialization sequences are interrupted or bypassed.
The operational impact of this vulnerability extends beyond simple application crashes to potentially enable more serious security consequences within environments where Nokogiri is deployed. Process termination due to NULL pointer dereferences can lead to denial of service conditions that may be exploited by malicious actors to disrupt services or cause system instability. In web applications processing untrusted input, this vulnerability could allow attackers to craft malformed XML or HTML documents that trigger the crash condition when parsed through Nokogiri's native components. Such scenarios present particular risk in high-availability systems where repeated crashes could lead to cascading failures across dependent services.
Security practitioners should prioritize immediate remediation by upgrading to Nokogiri version 1.19.4, which includes patches addressing the uninitialized object handling behavior. The fix implemented in this release properly initializes native wrapper classes before method invocation and includes additional validation checks that prevent NULL pointer dereference conditions during object lifecycle management. Organizations maintaining applications that depend on older versions of Nokogiri should conduct thorough testing to ensure compatibility with the security patch while monitoring for any potential side effects from the updated initialization routines. This vulnerability demonstrates the importance of proper memory management in mixed-language environments and serves as a reminder of the critical nature of validating object states before method execution in native extensions that interface with high-level scripting languages like Ruby. The ATT&CK framework categorizes this type of vulnerability under privilege escalation techniques through memory corruption, highlighting its potential for broader exploitation beyond simple denial of service scenarios.