CVE-2015-8776 in C Library
Summary
by MITRE
The strftime function in the GNU C Library (aka glibc or libc6) before 2.23 allows context-dependent attackers to cause a denial of service (application crash) or possibly obtain sensitive information via an out-of-range time value.
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Analysis
by VulDB Data Team • 07/25/2022
The vulnerability identified as CVE-2015-8776 represents a critical flaw in the GNU C Library's implementation of the strftime function, affecting versions prior to 2.23. This issue resides within the core system library that forms the foundation of countless Linux and Unix-based applications, making it a particularly dangerous weakness that can cascade through entire software ecosystems. The vulnerability manifests when the strftime function processes time values that fall outside the expected range, creating unpredictable behavior that can be exploited by malicious actors to disrupt system operations or potentially extract sensitive data from memory.
The technical root cause of this vulnerability stems from inadequate input validation within the strftime implementation, which fails to properly handle out-of-range time values that exceed the normal bounds of valid time representations. When an application calls strftime with such invalid parameters, the function can traverse memory locations beyond its intended boundaries, leading to either segmentation faults that crash the application or, in more sophisticated exploitation scenarios, information disclosure through memory leaks. This flaw operates at the system level rather than application level, meaning that any software relying on glibc's strftime function could be compromised, regardless of the specific application's own security measures.
The operational impact of CVE-2015-8776 extends far beyond simple denial of service conditions, as it can potentially enable information disclosure attacks that compromise system security. Attackers can leverage this vulnerability to cause applications to crash repeatedly, effectively creating persistent denial of service conditions that can disrupt critical services. More concerning is the potential for sensitive information extraction, where the improper memory handling could expose kernel memory contents, credentials, or other confidential data to unauthorized parties. This vulnerability particularly affects web servers, database applications, and any system components that process time-based data or generate time-stamped output, making it a prime target for attackers seeking to exploit system instability or extract valuable information.
Security practitioners should immediately prioritize patching affected systems to address this vulnerability, as the glibc library is fundamental to nearly all Linux-based systems and applications. The recommended mitigation strategy involves upgrading to glibc version 2.23 or later, which includes proper bounds checking and input validation for the strftime function. Organizations should also implement monitoring for unusual application crashes or restart patterns that might indicate exploitation attempts, as well as review application code for potential reliance on vulnerable strftime calls. This vulnerability aligns with CWE-129, which describes improper validation of array indices, and maps to ATT&CK technique T1499.004 for denial of service through resource exhaustion, while also potentially supporting information gathering techniques through memory disclosure mechanisms. System administrators must ensure comprehensive testing of patches in development environments before deployment to avoid disrupting legitimate application functionality while maintaining the security posture against this and related time-based exploitation vectors.