CVE-2014-9130 in LibYAML
Summary
by MITRE
scanner.c in LibYAML 0.1.5 and 0.1.6, as used in the YAML-LibYAML (aka YAML-XS) module for Perl, allows context-dependent attackers to cause a denial of service (assertion failure and crash) via vectors involving line-wrapping.
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Analysis
by VulDB Data Team • 04/07/2022
The vulnerability identified as CVE-2014-9130 represents a critical denial of service flaw within LibYAML versions 0.1.5 and 0.1.6, specifically affecting the YAML-LibYAML Perl module also known as YAML-XS. This issue manifests through a context-dependent assertion failure that ultimately leads to application crashes, fundamentally compromising system availability and stability. The vulnerability stems from improper handling of line-wrapping scenarios during YAML parsing operations, creating a condition where maliciously crafted input can trigger unexpected program termination. The flaw exists in the scanner.c component of the library, which is responsible for tokenizing and scanning YAML input streams, making it a core element in the parsing pipeline that directly impacts the module's reliability and security posture.
The technical implementation of this vulnerability involves the scanner component's inadequate validation of line-wrapping sequences within YAML documents. When processing input containing specific line-wrapping patterns, the parser encounters a condition that violates internal assertions, causing the program to terminate abruptly rather than gracefully handling the malformed input. This behavior aligns with CWE-617, which describes reachable assertions that can be triggered by external inputs, and represents a classic example of improper input validation leading to denial of service conditions. The vulnerability demonstrates how seemingly benign text formatting operations can be exploited to disrupt service availability, particularly when the input processing logic fails to account for edge cases in line termination handling.
From an operational perspective, this vulnerability poses significant risks to systems that rely on YAML parsing for configuration management, data exchange, or application initialization. The denial of service impact extends beyond simple application crashes to potentially affect entire service availability, especially in environments where YAML processing is integral to system operations. Attackers can exploit this vulnerability by crafting YAML documents with specific line-wrapping patterns that trigger the assertion failure, causing the affected Perl applications to crash and potentially requiring manual intervention to restore service. The context-dependent nature of the vulnerability means that exploitation requires specific input patterns that are carefully crafted to trigger the precise conditions leading to the assertion failure, making it moderately difficult to exploit but highly impactful when successful.
The mitigation strategies for CVE-2014-9130 primarily involve upgrading to LibYAML version 0.1.7 or later, which contains the necessary patches to address the scanner.c assertion failure. Organizations should also implement input validation measures that sanitize YAML content before processing, particularly when dealing with untrusted input sources. Additionally, deploying application-level monitoring and alerting systems can help detect unusual crash patterns that may indicate exploitation attempts. The vulnerability's classification under ATT&CK technique T1499.004, which covers network denial of service, highlights the importance of robust input handling and proper error management in preventing such attacks. Security teams should also consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts, while maintaining regular vulnerability assessments to identify similar issues in other components of their YAML processing infrastructure.