CVE-2015-1472 in C Library
Summary
by MITRE
The ADDW macro in stdio-common/vfscanf.c in the GNU C Library (aka glibc or libc6) before 2.21 does not properly consider data-type size during memory allocation, which allows context-dependent attackers to cause a denial of service (buffer overflow) or possibly have unspecified other impact via a long line containing wide characters that are improperly handled in a wscanf call.
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Analysis
by VulDB Data Team • 03/11/2022
The vulnerability identified as CVE-2015-1472 resides within the GNU C Library implementation of the ADDW macro in the stdio-common/vfscanf.c file, affecting glibc versions prior to 2.21. This flaw represents a critical memory management issue that manifests during the processing of wide character input streams through wscanf function calls. The vulnerability specifically targets the improper handling of data-type size considerations during memory allocation operations, creating a condition where attackers can manipulate input streams to trigger unexpected behavior in the underlying library functions. The flaw operates at the intersection of input validation and memory management, creating a pathway for exploitation that leverages the library's handling of wide character sequences within formatted input operations.
The technical mechanism behind this vulnerability involves the ADDW macro's failure to correctly account for data-type sizes when allocating memory buffers for wide character processing. When a wscanf call processes input containing long sequences of wide characters, the macro's memory allocation logic does not properly scale the allocated buffer size according to the actual data type requirements. This mismatch causes the library to either allocate insufficient memory for the wide character data or to miscalculate the required buffer space, leading to buffer overflow conditions that can corrupt adjacent memory regions. The vulnerability is particularly insidious because it only manifests under specific conditions involving long input lines containing wide characters, making it difficult to detect through standard testing procedures and allowing attackers to craft precise payloads that trigger the flaw.
The operational impact of CVE-2015-1472 extends beyond simple denial of service scenarios to potentially encompass arbitrary code execution or information disclosure depending on the system configuration and attack vector. When exploited successfully, the buffer overflow can corrupt critical memory structures including stack canaries, return addresses, or heap metadata, potentially enabling attackers to redirect program execution flow or extract sensitive information from memory. The context-dependent nature of this vulnerability means that exploitation requires specific input conditions but can be reliably triggered in applications that rely on glibc's wscanf functionality for processing user input. This makes the vulnerability particularly dangerous in applications that process untrusted input streams, such as web applications, network services, or any software that accepts wide character input from external sources.
Mitigation strategies for CVE-2015-1472 focus primarily on upgrading to glibc version 2.21 or later, where the memory allocation logic has been corrected to properly consider data-type sizes during buffer allocation. System administrators should prioritize patching affected systems and verifying that all applications relying on glibc's scanf family functions are updated to use patched library versions. Additional defensive measures include implementing input validation controls that limit the length of input streams processed by wscanf functions, applying address space layout randomization techniques to make exploitation more difficult, and monitoring system logs for unusual input patterns that might indicate attempted exploitation. The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and can be mapped to ATT&CK technique T1059.007 for the execution of malicious code through command-line interfaces that might leverage the library vulnerability. Organizations should also consider implementing application sandboxing and privilege separation to limit the potential impact of successful exploitation attempts.