CVE-2023-38545: 
vulnerability analysis and mitigation

CVE-2023-38545 is a high-severity heap buffer overflow vulnerability discovered in curl's SOCKS5 proxy handshake functionality. The vulnerability affects curl versions between 7.69.0 and 8.3.0, disclosed on October 11, 2023. When curl is configured to use SOCKS5 proxy with remote hostname resolution, a buffer overflow can occur if the hostname exceeds 255 bytes (Curl Advisory).

The vulnerability occurs during the SOCKS5 proxy handshake when curl is asked to pass a hostname to the SOCKS5 proxy for address resolution. While curl normally switches to local name resolving if the hostname exceeds 255 bytes, a bug in the state machine can cause the wrong value to be set for the hostname resolution control variable during a slow SOCKS5 handshake. This results in copying the oversized hostname to a heap-based buffer instead of the resolved address. The vulnerability has a CVSS v3.1 base score of 9.8 CRITICAL (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) (NVD).

Successful exploitation of this vulnerability could lead to remote code execution, allowing attackers to execute arbitrary code on affected systems. The vulnerability affects both the curl command-line tool (when used with specific rate limiting settings) and applications using libcurl. The impact is particularly severe for REST API clients, package managers, web scraping tools, IoT devices, and CI/CD pipelines that rely on curl for web interactions (SecPod).

The primary mitigation is to upgrade to curl version 8.4.0 or later, which fixes the vulnerability. Alternative workarounds include: avoiding the use of CURLPROXYSOCKS5HOSTNAME proxies with curl, not setting proxy environment variables to socks5h://, or ensuring the CURLOPTBUFFERSIZE is set larger than 65,541 bytes. For applications using libcurl, the CURLOPTBUFFERSIZE option can be used to adjust the buffer size (Curl Advisory).

The vulnerability has received significant attention from major technology companies, with Apple, Microsoft, and various Linux distributions releasing security updates to address the issue. NetApp and other vendors have issued security advisories for their affected products (NetApp Advisory, Microsoft Q&A).