CVE-2019-18197 in Java SE
Summary
by MITRE
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.
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Analysis
by VulDB Data Team • 05/29/2026
The vulnerability identified as CVE-2019-18197 resides within the libxslt library version 1.1.33, specifically within the xsltCopyText function located in the transform.c file. This issue represents a classic memory safety flaw that demonstrates the dangers of improper pointer management in XML processing libraries. The vulnerability occurs when a pointer variable fails to be properly reset during certain execution paths, creating a scenario where memory management operations can lead to unpredictable behavior. The flaw is particularly concerning because it operates at the intersection of memory allocation, pointer arithmetic, and buffer boundary checking, making it a sophisticated target for exploitation.
The technical nature of this vulnerability stems from a missing pointer reset operation that should occur under specific conditional circumstances during XSLT transformation processing. When the relevant memory area undergoes deallocation and subsequent reuse, the uninitialized pointer can point to memory locations outside the intended buffer boundaries. This condition creates two primary attack vectors: the potential for writing data beyond the allocated buffer limits, which could lead to memory corruption and arbitrary code execution, and the risk of information disclosure through uninitialized data exposure. The vulnerability's impact is amplified by the fact that XSLT processing is commonly used in web applications and XML parsing systems, making it a potentially widespread concern across numerous software platforms.
From an operational perspective, this vulnerability presents significant risks to systems that process untrusted XML data through libxslt libraries. The attack surface is broad as XSLT transformations are integral to many web applications, content management systems, and enterprise software that handle XML data from external sources. An attacker could potentially exploit this flaw by crafting malicious XML documents that trigger the specific memory management conditions required to activate the vulnerability. The bounds check failure creates opportunities for both denial of service attacks through memory corruption and more sophisticated exploitation techniques that could lead to privilege escalation or remote code execution depending on the target system's configuration and memory layout. The vulnerability's classification aligns with CWE-121, which addresses stack-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read vulnerabilities, making it a multi-faceted memory safety concern.
The mitigation strategies for CVE-2019-18197 primarily involve updating to patched versions of libxslt where the pointer reset logic has been corrected to properly handle the memory management conditions. System administrators should prioritize patching affected installations, particularly those handling untrusted XML input, as the vulnerability can be exploited remotely without authentication. Additional defensive measures include implementing strict input validation for XML data, using sandboxed processing environments, and employing memory protection mechanisms such as address space layout randomization and stack canaries. Organizations should also consider implementing network segmentation and monitoring for unusual XML processing patterns that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1059.007 for script-based execution and potentially T1557.001 for remote code execution, highlighting the need for comprehensive security monitoring and incident response procedures. Given the library's widespread use in enterprise environments, organizations should conduct thorough vulnerability assessments to identify all systems utilizing affected versions of libxslt and ensure complete remediation across their infrastructure.