CVE-2025-0633 - Heap-Based Buffer Overflow in iniparser Exposes Sensitive Memory

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In February 2025, a new security vulnerability was discovered in the popular C library iniparser, which is used for parsing .ini configuration files. This vulnerability, tracked as CVE-2025-0633, exposes a serious heap-based buffer overflow flaw in the iniparser_dumpsection_ini() function. This post explains the vulnerability, provides real-world code snippets, and demonstrates how an attacker could exploit this flaw to read sensitive information from process memory.

What Is iniparser?

iniparser is a lightweight C library to parse .ini files, which are commonly used for configuration in software projects. Many open-source projects use iniparser due to its simplicity and speed.

What Is CVE-2025-0633?

CVE-2025-0633 is a heap-based buffer overflow in the iniparser_dumpsection_ini() function. This means a specially crafted section name or key/value in an .ini file can cause the function to write or read beyond the bounds of allocated memory.

Impact:

- Attackers can potentially read sensitive data from the heap, including environment variables, credentials, or leftovers from other heap allocations.

Vulnerable Code

Let’s look at a simplified version of the vulnerable function in iniparser (as found in iniparser 4.2):

void iniparser_dumpsection_ini(FILE *f, dictionary *d, const char *section) {
    char key[256];
    int i;

    snprintf(key, sizeof(key), "%s:", section);

    for(i =  ; i < d->size ; i++) {
        if(/* compare section name prefix */) {
            fprintf(f, "%s=%s\n", d->key[i], d->val[i]);
        }
    }
}

snprintf() is used to write the section name and a colon into the buffer key.

- If section (taken directly from the .ini file) is longer than 255 characters, the null terminator can be written out of bounds.
- Furthermore, the code could use this overflowed key buffer later, leading to out-of-bounds reads or writes.

An attacker can craft an .ini section with an over-long name, such as

[AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA....] ; (more than 255 As)
foo=bar

Pass input to the vulnerable program: The program using iniparser reads this file.

3. Reach dump function: Attack code path where iniparser_dumpsection_ini() is called (some programs dump to logs, or expose API endpoints that trigger this).
4. Out-of-bounds read: When the buffer overflows, following code may read data from the heap surrounding the overflowed buffer. This data could include memory from previous allocations such as passwords or API tokens—information an attacker should not see.

ini.conf (malicious file)

[AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA...repeat until >255...]
attackkey=attackvalue

Vulnerable program

#include <stdio.h>
#include "iniparser.h"

int main(int argc, char *argv[]) {
    dictionary *ini = iniparser_load(argv[1]);
    iniparser_dumpsection_ini(stdout, ini, "A... (very long)");
    iniparser_freedict(ini);
    return ;
}

What Happens?

- When run, the process will overflow the buffer and read or print contents from heap memory outside the intended buffer, visibly leaking out-of-bounds data on the standard output or log files.

How to Fix

The maintainers patched the issue in commit af12f43, by:

Patch snippet

if (strlen(section) >= sizeof(key) - 2) {
    // Section name is too long
    return;
}
snprintf(key, sizeof(key), "%s:", section);

References

- Official CVE Record (CVE-2025-0633)
- iniparser GitHub Repository
- Patch for Issue
- Openwall Linux Security List

Conclusion

CVE-2025-0633 is a dangerous bug in iniparser that might let attackers read secret memory from programs using this library. To protect your applications, update iniparser to the latest version as soon as possible, or apply the provided patch manually.

If you want to check your software:

Timeline

Published on: 02/19/2025 07:15:33 UTC