CVE-2015-9019 in libxslt
Summary
by MITRE
In libxslt 1.1.29 and earlier, the EXSLT math.random function was not initialized with a random seed during startup, which could cause usage of this function to produce predictable outputs.
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Analysis
by VulDB Data Team • 08/25/2020
The vulnerability identified as CVE-2015-9019 affects libxslt versions 1.1.29 and earlier, specifically targeting the EXSLT math.random function implementation. This flaw represents a significant security weakness in XML stylesheet processing libraries that are widely used across various applications and systems. The issue stems from improper initialization of the random number generation mechanism within the library's mathematical functions, creating predictable output patterns that undermine the fundamental security properties expected from cryptographic random number generators.
The technical root cause of this vulnerability lies in the failure to properly seed the random number generator during library initialization. When the EXSLT math.random function is invoked, it relies on an underlying random number generation algorithm that requires proper seeding to ensure unpredictability of outputs. Without adequate seeding, the function produces sequences of numbers that follow predictable patterns, making it susceptible to analysis and exploitation by adversaries who can potentially reverse-engineer the generation process. This flaw falls under the category of weak random number generation as classified by CWE-330, which specifically addresses the use of insufficiently random values in security-sensitive contexts. The vulnerability represents a direct violation of cryptographic best practices and can be categorized under the ATT&CK technique T1083 for the discovery of system information, as it enables adversaries to predict outputs that should remain unpredictable.
The operational impact of CVE-2015-9019 extends beyond simple predictability concerns, as it can enable various attack vectors that compromise system security. Applications utilizing libxslt for processing XML documents may inadvertently expose sensitive information or create predictable outputs that can be exploited in cryptographic attacks, session prediction, or other security-sensitive contexts. The vulnerability affects systems where random number generation is critical for security purposes, such as generating session identifiers, cryptographic keys, or other security tokens that rely on the math.random function. When exploited, this vulnerability can lead to privilege escalation, unauthorized access, or information disclosure attacks, particularly in environments where predictable outputs could be leveraged to bypass security controls or predict system behavior.
Mitigation strategies for CVE-2015-9019 primarily involve upgrading to libxslt version 1.1.30 or later, where the random number generator initialization issue has been resolved. System administrators should conduct comprehensive vulnerability assessments to identify all systems utilizing affected versions of libxslt and prioritize remediation efforts accordingly. Additionally, organizations should implement monitoring and logging mechanisms to detect unusual patterns in random number usage that might indicate exploitation attempts. Security teams should also consider implementing additional controls such as input validation, output sanitization, and access controls around XML processing functions to reduce the potential impact of any remaining vulnerabilities. The fix addresses the core initialization issue by ensuring proper seeding of the random number generator during library startup, thereby restoring the expected entropy and unpredictability of the math.random function outputs.