Learn about the Format String vulnerability (CWE-134) and its implications. Understand its origins, manifestations, and ways to prevent exploitation.

CWE-635: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CWE-726: Weaknesses Associated with OWASP Top Ten (2004)

CWE-743: Weaknesses in Input Output (FIO) of CERT C Standard

CWE-808: Top 25 Most Dangerous Programming Errors Nominee List

CWE-845: Input Validation and Data Sanitization Weaknesses

CWE-865: Risky Resource Management

CWE-877: Weaknesses in Input Output Section of CERT C++ Standard

CWE-884: Multitude of Weaknesses with Broad Impacts

CWE-990: Detection of Tainted Input to Command Cluster

CWE-1131: Software Security Decrease with CISQ Quality Measures

CWE-1134: Input Validation and Data Sanitization Weaknesses

CWE-1163: Weaknesses in Input Output Section of SEI CERT C Coding Standard

CWE-1179: Drawbacks in Input Validation and Data Sanitization (IDS)

CWE-1308: Security Weaknesses in CISQ Quality Measures

CWE-1340: SMM Representation of Automated Source Code Data Protection

CWE-1399: Weaknesses Related to Memory Safety

Explore CWE-134, the Format String vulnerability that emerged in 1999. Discover prevention tips to safeguard your application's integrity against exploitation.

CWE-134: Format String Vulnerability - Origins & Prevention

Format String vulnerabilities, although often classified as Buffer Overflow, do not involve overflowing buffers. The Format String vulnerability emerged around 1999 and arises from the difficulty of a function with a variable number of arguments in determining the exact number of passed arguments. The printf() family of functions, commonly used for variable arguments, including C-runtime functions, are frequently affected. Various manifestations of the Format String issue exist. A dangerous scenario is when a *printf() call lacks a format specifier, making it exploitable. For example, printf(input); is exploitable, whereas printf(y, input); is not exploitable in that context. In the first call, if used incorrectly, an attacker can gain access to stack memory since the input string acts as the format specifier. By injecting format specifiers into the input string, the attacker can read stack values as the remaining parameters are retrieved from the stack. In the worst case, this misuse can grant enough control for arbitrary values to be written into the program's memory, be it a single value or multiple values as in an exploitation program. Commonly targeted entities include file names, process names, and identifiers. Format string issues, a classic problem in C/C++, have become relatively rare due to their discoverability. One of the main reasons these vulnerabilities are exploitable is the %n operator, which writes the count of characters printed so far by the format string to the memory pointed to by its argument. By skillfully crafting a format string, a malicious user can utilize stack values to establish a write-what-where condition, enabling the execution of arbitrary code. Other operators could also be exploited, such as the %9999s operator, which could trigger a buffer overflow or generate larger outputs than intended in functions like fprintf, specifically designed for formatting files.

CWE-134: Format String Vulnerability

CWE-134: Format String Vulnerability

Is your System Free of Underlying Vulnerabilities? Find Out Now

Is your System Free of Underlying Vulnerabilities?
Find Out Now