{"document":{"category":"csaf_vex","csaf_version":"2.0","title":"CVE-2026-56123: socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser","publisher":{"category":"vendor","name":"HarborGuard Database","namespace":"https://database.harborguard.co"},"tracking":{"id":"CVE-2026-56123","status":"final","version":"1","initial_release_date":"2026-06-25T15:43:19.580Z","current_release_date":"2026-06-25T15:43:19.580Z","revision_history":[{"date":"2026-06-25T15:43:19.580Z","number":"1","summary":"Initial machine-readable export from HarborGuard."}]},"distribution":{"tlp":{"label":"WHITE"},"text":"Public CVE data; freely redistributable."},"notes":[{"category":"description","text":"socat versions 1.8.0.0 through 1.8.1.1 contain a heap-based buffer overflow vulnerability that allows a malicious SOCKS5 proxy server to overwrite adjacent heap memory by exploiting a sign-extension flaw in the DOMAINNAME reply parser. During connection setup, the domain name length byte is read through a signed char field causing a negative bytes_to_read value that is implicitly converted to size_t, resulting in an unbounded heap write into the 262-byte reply buffer with attacker-controlled size and content.","title":"CVE description"}],"references":[{"category":"self","summary":"CVE-2026-56123 on HarborGuard Database","url":"https://database.harborguard.co/cve/CVE-2026-56123"},{"category":"external","summary":"CVE Record","url":"https://www.cve.org/CVERecord?id=CVE-2026-56123"},{"category":"external","summary":"dest-unreach.org","url":"http://www.dest-unreach.org/socat/CHANGES"},{"category":"external","summary":"vulncheck.com","url":"https://www.vulncheck.com/advisories/socat-heap-buffer-overflow-via-socks5-reply-parser"}]},"product_tree":{"branches":[{"category":"vendor","name":"socat","branches":[{"category":"product_name","name":"socat","branches":[{"category":"product_version_range","name":">=1.8.0.0 <1.8.1.2","product":{"name":"socat socat >=1.8.0.0 <1.8.1.2","product_id":"CSAFPID-1","product_identification_helper":{"cpe":"cpe:2.3:a:socat:socat:*:*:*:*:*:*:*:*"}}}]}]}]},"vulnerabilities":[{"cve":"CVE-2026-56123","title":"socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser","notes":[{"category":"description","text":"socat versions 1.8.0.0 through 1.8.1.1 contain a heap-based buffer overflow vulnerability that allows a malicious SOCKS5 proxy server to overwrite adjacent heap memory by exploiting a sign-extension flaw in the DOMAINNAME reply parser. During connection setup, the domain name length byte is read through a signed char field causing a negative bytes_to_read value that is implicitly converted to size_t, resulting in an unbounded heap write into the 262-byte reply buffer with attacker-controlled size and content.","title":"CVE description"}],"product_status":{"known_affected":["CSAFPID-1"]},"scores":[{"cvss_v4":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N","baseScore":9.2,"baseSeverity":"CRITICAL"},"products":["CSAFPID-1"]}],"remediations":[{"category":"vendor_fix","details":"Update to a fixed version: 1.8.1.2.","product_ids":["CSAFPID-1"],"url":"http://www.dest-unreach.org/socat/CHANGES"}]}]}