CVE-2023-25139 in C Library
Summary
by MITRE • 02/03/2023
sprintf in the GNU C Library (glibc) 2.37 has a buffer overflow (out-of-bounds write) in some situations with a correct buffer size. This is unrelated to CWE-676. It may write beyond the bounds of the destination buffer when attempting to write a padded, thousands-separated string representation of a number, if the buffer is allocated the exact size required to represent that number as a string. For example, 1,234,567 (with padding to 13) overflows by two bytes.
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Analysis
by VulDB Data Team • 03/26/2025
The vulnerability identified as CVE-2023-25139 represents a critical buffer overflow flaw within the GNU C Library's sprintf function implementation in glibc version 2.37. This issue manifests as an out-of-bounds write condition that occurs under specific circumstances involving formatted string output operations, making it particularly insidious as it can exploit seemingly correct buffer sizing. The vulnerability specifically affects scenarios where applications use padding specifications combined with thousands separators during numeric formatting, creating a situation where the library writes beyond the allocated buffer boundaries despite the buffer being precisely sized for the content.
The technical flaw arises from the sprintf function's handling of formatted numeric strings when padding is applied to numbers that include thousands separators. When a number such as 1,234,567 is formatted with padding to a width of 13 characters, the glibc implementation incorrectly calculates the required buffer space, resulting in an overflow of exactly two bytes beyond the intended destination buffer. This behavior occurs regardless of whether the buffer is allocated with the correct size needed to represent the formatted string, making the vulnerability particularly dangerous as it can bypass typical buffer size validation checks. The issue stems from improper boundary calculations within the formatting logic rather than fundamental memory management failures, which distinguishes it from similar vulnerabilities categorized under CWE-676.
The operational impact of this vulnerability extends across numerous applications and systems that rely on glibc's sprintf function for formatted output operations, particularly those involving financial calculations, data logging, or any scenario where numeric formatting with padding and thousands separators is employed. Attackers could potentially exploit this vulnerability to achieve arbitrary code execution or cause application crashes by carefully crafting input that triggers the overflow condition. The vulnerability's exploitation requires a specific combination of formatting parameters and buffer sizing, but given the widespread use of sprintf in system libraries and applications, the potential attack surface remains extensive. This flaw particularly affects systems running glibc 2.37 where applications perform formatted numeric output with padding specifications, creating opportunities for both denial-of-service attacks and more sophisticated exploitation techniques.
Mitigation strategies for CVE-2023-25139 primarily involve updating to patched versions of glibc where the buffer overflow has been corrected through improved boundary checking and memory allocation calculations. System administrators should prioritize applying security updates from their respective distribution vendors as soon as patches become available, particularly in environments where applications process untrusted input through sprintf operations. Additional defensive measures include implementing robust input validation and sanitization practices, monitoring for unusual sprintf usage patterns, and employing address space layout randomization techniques to complicate potential exploitation attempts. Organizations should also consider implementing runtime protections such as stack canaries and heap metadata validation to detect and prevent exploitation attempts. This vulnerability aligns with ATT&CK technique T1059.007 for command and scripting interpreter usage, as exploitation may involve crafting malicious input to trigger the buffer overflow, and T1555.003 for credentials from password storage components, as successful exploitation could potentially lead to privilege escalation or credential compromise. The issue demonstrates the importance of thorough testing of standard library functions under various input conditions and highlights the need for continuous security assessment of core system components.