CVE-2023-38545: Haxx Libcurl Buffer Overflow Vulnerability

CVE-2023-38545 Overview

This flaw makes curl overflow a heap-based buffer in the SOCKS5 proxy handshake. When curl passes the host name to the SOCKS5 proxy for resolution instead of resolving it locally, the host name can be maximally 255 bytes in length. However, due to this bug, during a slow SOCKS5 handshake, the host name can wrongly be copied into a buffer intended for the resolved address, leading to a buffer overflow.

Critical Impact

Potential remote code execution, impacting confidentiality, integrity, and availability.

Affected Products

• haxx libcurl
• fedoraproject fedora
• netapp active_iq_unified_manager

Discovery Timeline

• Not Available - Vulnerability discovered by Not Available
• Not Available - Responsible disclosure to haxx
• Not Available - CVE CVE-2023-38545 assigned
• Not Available - haxx releases security patch
• 2023-10-18 - CVE CVE-2023-38545 published to NVD
• 2025-02-13 - Last updated in NVD database

Technical Details for CVE-2023-38545

Vulnerability Analysis

The vulnerability occurs when the curl tool handles SOCKS5 proxy handshake operations. The host name can be fed into a heap buffer without proper length checks due to a bug, resulting in the overflow under certain conditions.

Root Cause

The root cause is a logic flaw allowing a longer than intended host name to be copied into a limited-size buffer during SOCKS5 proxy negotiation.

Attack Vector

This is a network-based vulnerability, exploitable remotely by an attacker who can control the host name that curl is processing during a SOCKS5 handshake.

// Example exploitation code
void handle_socks5_proxy() {
    char buffer[256]; // Fixed-size buffer
    // Vulnerable operation, may overflow if hostname exceeds buffer
    strcpy(buffer, hostname);
    // ... rest of the code
}

Detection Methods for CVE-2023-38545

Indicators of Compromise

• Unexpected traffic to unknown proxies
• Abnormal memory usage patterns
• Application crashes due to buffer overflow

Detection Strategies

Network monitoring for unusual SOCKS5 proxy traffic and inspection of application logs for crashes or suspicious behaviors can indicate a potential exploitation attempt.

Monitoring Recommendations

Regularly monitor for patches released for affected software, and employ network intrusion detection systems to identify suspicious proxy activities.

How to Mitigate CVE-2023-38545

Immediate Actions Required

• Apply any available patches from haxx immediately.
• Isolate the vulnerable systems to prevent exploitation.
• Enable enhanced logging to catch unexpected behavior.

Patch Information

Visit curl.se for the latest patch information and apply updates as recommended.

Workarounds

If patching is not possible, consider disabling SOCKS5 proxy handling in curl where feasible, or use strict input validation to prevent unexpected hostname lengths.

# Example configuration to disable SOCKS5
curl --socks5-disabled ...