CVE-2024-35329 in libyaml
Summary
by MITRE • 06/11/2024
libyaml 0.2.5 is vulnerable to a heap-based Buffer Overflow in yaml_document_add_sequence in api.c. NOTE: the supplier disputes this because the finding represents a user error. The problem is that the application, which was making use of the libyaml library, omitted the required calls to the yaml_document_initialize and yaml_document_delete functions.
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Analysis
by VulDB Data Team • 08/03/2026
The vulnerability in libyaml version 0.2.5 represents a heap-based buffer overflow condition that occurs within the yaml_document_add_sequence function located in the api.c file. This issue manifests when applications fail to properly initialize document structures before attempting to add sequence elements, creating a scenario where memory operations exceed allocated boundaries. The root cause stems from improper memory management practices within the library's API implementation, where the absence of required initialization calls creates a state where subsequent operations attempt to write beyond allocated heap memory regions.
From a technical perspective, the vulnerability operates through a classic buffer overflow mechanism where the yaml_document_add_sequence function does not adequately validate or check the document structure's readiness before performing memory writes. The function assumes that the underlying document has been properly initialized with yaml_document_initialize calls, but when this prerequisite is omitted, the internal data structures remain in an undefined state. This undefined state leads to unpredictable memory access patterns where sequence elements are written to locations outside the intended heap buffers, potentially allowing attackers to overwrite adjacent memory regions or trigger memory corruption that could be exploited for arbitrary code execution.
The operational impact of this vulnerability extends beyond simple application crashes to potential security implications when applications improperly handle yaml document processing. While the vendor disputes the classification as a security vulnerability due to user error, the practical reality is that such errors can occur in complex applications or during rapid development cycles where proper API usage documentation may be overlooked. The vulnerability becomes particularly concerning in environments where libyaml is used for parsing untrusted input data, as improper document handling could provide attack vectors for memory corruption exploits.
The flaw aligns with CWE-121 and CWE-122 categories from the Common Weakness Enumeration catalog, specifically addressing issues related to insufficient buffer bounds checking and improper memory management. From an ATT&CK framework perspective, this vulnerability could be leveraged as part of a broader attack chain under techniques such as T1059 for command execution or T1068 for local privilege escalation if exploited successfully. The vulnerability also relates to T1210 which covers exploitation of remote services through buffer overflows and memory corruption.
Mitigation strategies should focus on comprehensive code review processes to ensure all applications using libyaml properly implement the required initialization sequence including yaml_document_initialize before any document manipulation functions are called. Developers must also implement proper error handling around document operations to detect and prevent invalid state transitions. Additionally, application developers should consider implementing static analysis tools or code scanning procedures that can identify missing API calls in yaml processing code. The library itself could benefit from improved error checking mechanisms that would provide more informative failure modes when initialization requirements are not met, rather than allowing undefined behavior to occur. Organizations should also maintain updated documentation and training materials regarding proper libyaml usage patterns to reduce the likelihood of improper implementation that leads to exploitable conditions.
The vulnerability demonstrates how seemingly benign API usage errors can create serious security implications when libraries do not adequately protect against misuse or provide clear error feedback mechanisms. While ultimately user error in API implementation, the vulnerability highlights the importance of robust defensive programming practices and comprehensive testing of library usage patterns in security-critical applications.