CVE-2024-2961: GNU C Library Buffer Overflow Vulnerability

CVE-2024-2961 Overview

The iconv() function in the GNU C Library versions 2.39 and older may overflow the output buffer passed to it by up to 4 bytes when converting strings to the ISO-2022-CN-EXT character set. This overflow could be leveraged to crash an application or overwrite adjacent variables, potentially leading to more severe security implications.

Critical Impact

This vulnerability can lead to application crashes or variable overwrites, risking further code execution in certain contexts.

Affected Products

• GNU C Library (glibc) 2.39 and older
• Not Available
• Not Available

Discovery Timeline

• Not Available - Vulnerability discovered by Unknown
• Not Available - Responsible disclosure to Not Available
• 2024-04-17 - CVE CVE-2024-2961 assigned
• Not Available - Vendor releases security patch
• 2024-04-17 - CVE CVE-2024-2961 published to NVD
• 2025-02-13 - Last updated in NVD database

Technical Details for CVE-2024-2961

Vulnerability Analysis

This buffer overflow occurs due to improper handling of string conversions to the ISO-2022-CN-EXT character set in the iconv() function. The vulnerability is classified under CWE-787: Out-of-Bounds Write.

Root Cause

The root cause is an inadequate boundary check in the iconv() implementation, causing the buffer overflow by up to 4 bytes.

Attack Vector

Local attack vector using crafted input to exploit the buffer overflow when strings are converted.

// Example exploitation code (sanitized)
#include <stdio.h>
#include <stdlib.h>
#include <iconv.h>

int main() {
    char input[] = "exploit_string";
    char output[10];
    iconv_t cd = iconv_open("ISO-2022-CN-EXT", "UTF-8");
    if (cd == (iconv_t)-1) {
        perror("iconv_open");
        return EXIT_FAILURE;
    }
    char *inbuf = input;
    char *outbuf = output;
    size_t inbytesleft = sizeof(input);
    size_t outbytesleft = sizeof(output);
    iconv(cd, &inbuf, &inbytesleft, &outbuf, &outbytesleft);
    iconv_close(cd);
    return 0;
}

Detection Methods for CVE-2024-2961

Indicators of Compromise

• Application crashes
• Unusual memory behavior
• Overwritten variables

Detection Strategies

Utilize Host Intrusion Detection Systems (HIDS) to monitor for abnormal application behavior and crashes. Implement logging and alerting mechanisms to detect anomalies in memory use around the invocation of iconv().

Monitoring Recommendations

Continuously monitor and log the usage patterns of iconv() especially for parameters passed during the conversion to ISO-2022-CN-EXT.

How to Mitigate CVE-2024-2961

Immediate Actions Required

• Update the affected glibc to a patched version as soon as it becomes available.
• Implement additional input validation to prevent anomalous data from reaching vulnerable functions.
• Monitor application behavior for signs of exploitation.

Patch Information

Refer to official glibc repository and distribution advisories for updates specifically addressing CVE-2024-2961.

Workarounds

If immediate patching is not possible, consider disabling the conversion to ISO-2022-CN-EXT where feasible, or use alternative libraries or methods for character conversion.

# Configuration example
sudo sed -i '/ISO-2022-CN-EXT/d' /etc/iconv_supported.list