CVE-2026-57438 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, XInclude substitution performed by Nokogiri::XML::Node#do_xinclude replaced each in place, freeing the include node along with its children (such as and its descendants) and any namespaces declared on them. If an application had already exposed one of those nodes or namespaces to Ruby, the corresponding Ruby object was left pointing at freed memory. Using the object could result in invalid reads or writes to memory. This vulnerability is fixed in 1.19.4.
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Analysis
by VulDB Data Team • 06/25/2026
The vulnerability in Nokogiri versions prior to 1.19.4 represents a critical memory safety issue that arises from improper handling of XInclude substitution operations within the XML processing library. This flaw specifically affects the Nokogiri::XML::Node#do_xinclude method which performs in-place replacement of XInclude elements during document processing. When an XInclude operation occurs, the original include node and all its descendant elements including namespace declarations are freed from memory while simultaneously being replaced with content from external sources. The vulnerability stems from the library's failure to properly manage object references during this replacement process.
The technical implementation of this flaw involves a classic use-after-free condition where Ruby objects that were previously exposed to application code continue to reference memory locations that have been deallocated. When applications had already obtained references to nodes or namespace declarations that were subsequently freed during XInclude processing, these Ruby objects become invalid pointers pointing to freed memory regions. This creates a scenario where any subsequent operations on these objects could trigger invalid memory reads or writes, potentially leading to application crashes, data corruption, or arbitrary code execution depending on the specific memory layout and access patterns.
The operational impact of this vulnerability extends beyond simple memory corruption issues as it represents a fundamental flaw in how Nokogiri manages object lifecycles during XML processing operations. Applications using affected versions of Nokogiri that process documents containing XInclude elements are at risk of experiencing unpredictable behavior, application instability, and potential security exploits. The vulnerability is particularly concerning because it can be triggered through normal XML parsing operations without requiring special conditions or malicious input beyond the presence of XInclude elements in processed documents. This makes it an attractive target for attackers seeking to exploit memory safety issues in web applications, content management systems, or any software that relies on Nokogiri for XML processing.
From a cybersecurity perspective, this vulnerability aligns with CWE-416 which describes use-after-free conditions and maps to several ATT&CK techniques including T1059 for command and scripting interpreter usage and potentially T1203 for Exploitation for Client Execution. The fix implemented in version 1.19.4 addresses the core issue by ensuring proper reference management during XInclude substitution operations, preventing the premature freeing of objects that may still be referenced by application code. Organizations should prioritize updating to Nokogiri 1.19.4 or later versions and conduct thorough testing of XML processing functionality to ensure no residual issues remain. Additionally, security teams should monitor for potential exploitation attempts targeting this vulnerability in environments where Nokogiri is used for processing untrusted XML content, particularly in web-facing applications or systems handling external data sources.