CWE-134: Use of Externally-Controlled Format String

Description

The product uses a function that accepts a format string as an argument, but the format string originates from an external source.

Potential Impact

Confidentiality: Read Memory
Integrity: Modify Memory

How to Fix

Requirements

Choose a language that is not subject to this flaw.

Implementation

Ensure that all format string functions are passed a static string which cannot be controlled by the user, and that the proper number of arguments are always sent to that function as well. If at all possible, use functions that do not support the %n operator in format strings. [REF-116] [REF-117]

Build and Compilation

Run compilers and linkers with high warning levels, since they may detect incorrect usage.

Detection Methods

Automated Static Analysis: This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives....
Black Box: Since format strings often occur in rarely-occurring erroneous conditions (e.g. for error message logging), they can be difficult to detect using black box methods. It is highly likely that many laten...
Automated Static Analysis - Binary or Bytecode: According to SOAR [REF-1479], the following detection techniques may be useful: Highly cost effective: Bytec...

Related Weaknesses

References

View on MITRE CWE Database →

Use of Externally-Controlled Format String