CVE-2021-28906 in libyang
Summary
by MITRE • 05/21/2021
In function read_yin_leaf() in libyang
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Analysis
by VulDB Data Team • 05/23/2021
The vulnerability identified as CVE-2021-28906 resides within the libyang library's function read_yin_leaf(), which processes YIN (YANG Input Notation) data structures used in network configuration and management protocols. This library serves as a critical component in parsing and validating YANG data models that define network service configurations, making it a prime target for attackers seeking to disrupt network operations or gain unauthorized access to network infrastructure. The flaw manifests in how the function handles certain input data structures, particularly when processing leaf nodes within YIN documents that may contain malformed or maliciously constructed elements.
The technical implementation of this vulnerability stems from inadequate input validation and memory handling within the read_yin_leaf() function. When processing YIN data, the function fails to properly validate the structure and content of leaf elements, allowing for potential buffer overflows or memory corruption scenarios. This weakness aligns with CWE-121, which addresses stack-based buffer overflow conditions, and CWE-787, which covers out-of-bounds write operations. The vulnerability can be exploited through crafted YIN input that manipulates the parsing logic to cause unintended memory access patterns, potentially leading to arbitrary code execution or denial of service conditions.
The operational impact of CVE-2021-28906 extends significantly across network infrastructure deployments that rely on libyang for configuration management and service provisioning. Network devices implementing YANG-based management protocols such as NETCONF or RESTCONF are particularly at risk, as these systems often use libyang for parsing configuration data received from management systems or network elements. Attackers could leverage this vulnerability to compromise network devices, potentially gaining unauthorized access to sensitive network configurations, disrupting service availability, or establishing persistent access points within network infrastructure. The vulnerability's exploitation could affect enterprise network equipment, routers, switches, and network management systems that utilize YANG data models for configuration and monitoring.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected libyang installations to the latest versions containing the fix for read_yin_leaf() function behavior. Organizations should implement network segmentation and access controls to limit exposure of systems running vulnerable versions of libyang, particularly those handling external configuration inputs. Input validation measures should be enhanced to filter malformed YIN data before processing, and network monitoring systems should be configured to detect anomalous patterns in configuration management traffic. The ATT&CK framework's T1059.007 technique for command and script injection and T1210 for exploitation of remote services should be considered when developing defensive measures, as these attack vectors align with potential exploitation methods of this vulnerability. Additionally, implementing robust configuration management practices and regularly updating network device software components can significantly reduce the risk surface for exploitation of this and similar vulnerabilities.