Heap-based Buffer Overflow in socat Affects Network Communication Security

CVE-2026-56123

What is CVE-2026-56123?

Versions 1.8.0.0 to 1.8.1.1 of socat are susceptible to a heap-based buffer overflow vulnerability. This flaw arises during the parsing of the DOMAINNAME reply in SOCKS5 proxy connections, where an incorrectly handled domain name length byte can lead to an erroneous negative bytes_to_read value. This value, when converted implicitly to a size_t, results in unbounded writes to a 262-byte reply buffer, potentially allowing an attacker to overwrite adjacent heap memory and control the content that is written.

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