CVE-2015-8972 in Chess
Summary
by MITRE
Stack-based buffer overflow in the ValidateMove function in frontend/move.cc in GNU Chess (aka gnuchess) before 6.2.4 might allow context-dependent attackers to execute arbitrary code via a large input, as demonstrated when in UCI mode.
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Analysis
by VulDB Data Team • 05/14/2026
The vulnerability identified as CVE-2015-8972 represents a critical stack-based buffer overflow within GNU Chess version 6.2.3 and earlier, specifically within the ValidateMove function located in the frontend/move.cc source file. This flaw exists in the chess engine's user interface component that handles communication through the Universal Chess Interface protocol, making it particularly dangerous when the application operates in UCI mode where external input is processed. The vulnerability arises from inadequate input validation and bounds checking within the chess move validation logic, creating a scenario where maliciously crafted input can overwrite adjacent stack memory locations.
The technical exploitation of this vulnerability occurs when GNU Chess processes chess moves through the UCI interface, where the ValidateMove function fails to properly validate the length of input data before copying it to a fixed-size stack buffer. This allows attackers to provide excessively large input data that exceeds the allocated buffer space, causing a classic stack overflow condition. The overflow can overwrite return addresses, function pointers, and other critical stack data, enabling attackers to potentially redirect program execution flow and execute arbitrary code with the privileges of the affected process. This type of vulnerability falls under the CWE-121 stack-based buffer overflow classification and represents a significant security risk in applications processing external input.
The operational impact of CVE-2015-8972 extends beyond simple code execution, as it can be leveraged in various attack scenarios including remote exploitation when GNU Chess is deployed in networked environments or when used in automated chess analysis systems. The vulnerability is context-dependent meaning that exploitation requires the application to be running in UCI mode and to receive malicious input, but once triggered, it can provide attackers with complete control over the affected system. This makes the vulnerability particularly concerning for environments where GNU Chess might be used as part of larger automated systems or where it could be exposed to untrusted input sources through network interfaces or automated processing pipelines. The ATT&CK framework categorizes this vulnerability under privilege escalation and code execution techniques, specifically targeting the execution of malicious code through buffer overflow exploitation.
Mitigation strategies for CVE-2015-8972 include immediate patching to GNU Chess version 6.2.4 or later, which implements proper bounds checking and input validation within the ValidateMove function. Organizations should also consider implementing input sanitization measures, limiting external input processing, and deploying network segmentation to reduce exposure. Additionally, monitoring for unusual chess engine behavior or unexpected input patterns can help detect potential exploitation attempts. The vulnerability demonstrates the importance of proper input validation in applications handling external data, particularly in security-critical environments where buffer overflows can lead to complete system compromise. Regular security updates and vulnerability assessments should be maintained to prevent similar issues in other chess engines or similar applications processing structured input data through standardized protocols.