socat 1.8.0.0 – 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser_CVE-2026-56123

{
    "lastseen": "",
    "description": "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.",
    "published": "2026-06-25T15:43:19.580Z",
    "modified": "2026-06-25T15:43:19.580Z",
    "type": "cve",
    "title": "socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser",
    "source": "VulnCheck",
    "references": "http://www.dest-unreach.org/socat/CHANGES\nhttps://www.vulncheck.com/advisories/socat-heap-buffer-overflow-via-socks5-reply-parser",
    "id": "CVE-2026-56123",
    "bulletinFamily": "",
    "cwe": [
        "CWE-122"
    ],
    "cvelist": null,
    "sourceData": "socat socat 1.8.0.0",
    "sourceHref": "",
    "cvss": {
        "score": 9.2,
        "severity": "CRITICAL",
        "vector": "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",
        "version": "4.0"
    },
    "cvss2": [],
    "cvss3": {
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        "baseScore": 0,
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        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
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    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "socat",
    "version": "1.8.0.0",
    "vendor": "socat",
    "ai_description": "Heap-based buffer overflow vulnerability in socat via SOCKS5 reply parser",
    "ai_severity": "Critical",
    "ai_vendor": "socat",
    "ai_product": "socat",
    "ai_version": "1.8.0.0 - 1.8.1.1",
    "ai_score": 9.2
}