CVE-2012-2114 in musl
Summary
by MITRE
Stack-based buffer overflow in fprintf in musl before 0.8.8 and earlier allows context-dependent attackers to cause a denial of service (crash) or possibly execute arbitrary code via a long string to an unbuffered stream such as stderr.
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Analysis
by VulDB Data Team • 02/20/2019
The vulnerability identified as CVE-2012-2114 represents a critical stack-based buffer overflow flaw within the musl libc library implementation of the fprintf function. This issue affects versions prior to 0.8.8 and demonstrates how seemingly routine formatting operations can become vectors for severe system compromise. The vulnerability specifically manifests when fprintf processes long strings directed toward unbuffered streams such as stderr, creating a condition where the stack memory layout becomes corrupted through improper buffer handling. The flaw operates at the intersection of memory management and string processing, where the library fails to properly validate the length of input strings against available stack buffer space, leading to potential memory corruption that can be exploited by malicious actors.
The technical exploitation of this vulnerability follows a well-established pattern that aligns with CWE-121, which categorizes stack-based buffer overflow conditions. Attackers can leverage this weakness by providing excessively long strings to fprintf calls targeting unbuffered output streams, causing the function to write beyond the allocated stack buffer boundaries. This overflow can result in the corruption of adjacent stack memory, potentially overwriting return addresses, function pointers, or other critical control data. The attack surface is particularly concerning because stderr is commonly used for error reporting and debugging output, making it a frequent target for exploitation in various applications that rely on musl libc for their runtime operations. The vulnerability's context-dependent nature means that successful exploitation requires specific conditions, including the use of unbuffered streams and sufficiently long input strings to trigger the overflow condition.
The operational impact of this vulnerability extends beyond simple denial of service scenarios to encompass potential arbitrary code execution capabilities. When the stack overflow occurs during fprintf operations, the corrupted memory can lead to unpredictable program behavior, system crashes, or more sinister outcomes where attackers can manipulate the program flow to execute malicious code. This vulnerability affects systems running affected versions of musl libc, which is commonly found in embedded systems, lightweight Linux distributions, and various networked applications where memory efficiency and minimal resource usage are prioritized. The implications are particularly severe for systems where applications may be processing untrusted input through fprintf operations, as this creates multiple potential entry points for exploitation. The vulnerability's presence in a foundational library like musl libc means that its impact ripples through numerous applications and systems that depend on this standard C library implementation.
Mitigation strategies for CVE-2012-2114 must address both immediate remediation and long-term architectural considerations. The primary and most effective solution involves upgrading to musl libc version 0.8.8 or later, where the buffer overflow vulnerability has been patched through improved input validation and buffer boundary checking mechanisms. System administrators should prioritize patching affected systems, particularly those running embedded environments or minimal Linux installations where musl libc is the primary C library implementation. Additional defensive measures include implementing proper input validation at application layers to prevent excessively long strings from reaching fprintf functions, utilizing address space layout randomization techniques, and employing stack canary mechanisms to detect potential buffer overflows. The vulnerability also highlights the importance of following secure coding practices as outlined in the ATT&CK framework's software exploitation tactics, emphasizing the need for robust input sanitization and memory management throughout application development processes. Organizations should conduct thorough vulnerability assessments to identify applications that may be indirectly affected by this flaw through their use of musl libc, ensuring comprehensive coverage of all system components that might be vulnerable to similar buffer overflow conditions.