CVE-2022-44321 - PicoC Version 3.2.2 Heap Buffer Overflow Vulnerability in LexSkipComment Function Exploit Details, Mitigations, and Patching Guide

PicoC is a well-renowned and highly compact C interpreter for scripting purposes that is designed specifically for integration into various environments and applications, offering flexibility and compatibility. A recent discovery has shed light on a heap buffer overflow vulnerability (CVE-2022-44321) within PicoC Version 3.2.2. The issue lies in the LexSkipComment function in the lex.c source file, which is responsible for discarding comments within the scanned C source code. This particular vulnerability could be exploited by potential attackers to cause crashes, corrupt the heap data, or even execute arbitrary code.

Code Snippet

/* lex.c */
/* Source file for the PicoC Lexical Analyzer */
...
void LexSkipComment(Picoc *pc, LexState *Lexer, int NextCh)
{
    while (1)
    {
        if (NextCh == EOF)
            ProgramFail(pc, Lexer, "premature end of comment");
	...
        else if (NextCh == '*' && !strncmp(Lexer->Pos, "/**/", 3))
        {
            Lexer->Pos += 3;
            break;
        }
	...
    }
}

This function showcases how potential buffer overflows may happen when processing multi-line comments (/* */) in the lexer component of PicoC. The vulnerability arises when the function fails to enforce proper bounds checks and memory constraints during the comment parsing process.

Exploit Details

The LexSkipComment function observes the source code and iterates through the characters until it reaches the start of a multi-line comment, determined by the '/*' symbol. The LexSkipComment function continues to search for the comment terminator '*/'. A heap buffer overflow is triggered when the function encounters a specially crafted sequence of characters that contain the terminator, followed by an arbitrary sequence of characters and another terminator.

The main problem lies within the 'strncmp' function, which does not properly handle the aforementioned specific conditions, leading to the heap buffer overflow vulnerability.

Original references

- PicoC GitHub Repository
- CVE-2022-44321
- NVD - CVE-2022-44321

Mitigations and Patching

To temporarily mitigate the impact of this vulnerability, developers and users should avoid processing untrusted C source code with PicoC Version 3.2.2, until a patch is made available. Upstream maintainers should enforce proper bounds checking and memory constraints during the comment parsing process to correct the vulnerability.

Conclusion

The heap buffer overflow vulnerability (CVE-2022-44321) discovered in PicoC Version 3.2.2 demands immediate attention for implementation of a proper patch and necessary mitigations to reduce the risk associated with malicious exploitation. Developers of PicoC-based applications should remain vigilant and promptly apply any forthcoming patches to ensure a safe and secure development environment.

Disclaimer: This information is provided for educational purposes only. The author holds no responsibility for the misuse of the information or any damages resulting from the actions taken based on the provided content.

Timeline

Published on: 11/08/2022 15:15:00 UTC
Last modified on: 11/08/2022 21:55:00 UTC