CVE-2026-56123 (GCVE-0-2026-56123)

Vulnerability from cvelistv5 – Published: 2026-06-25 15:43 – Updated: 2026-06-26 02:03 X_Open Source
VLAI
Title
socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser
Summary
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.
Severity
9.2 (Critical)
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
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
  • CWE-122 - Heap-based Buffer Overflow
Assigner
References
Impacted products
Vendor Product Version
socat socat Affected: 1.8.0.0 , < 1.8.1.2 (custom)
Create a notification for this product.
Date Public
2026-06-25 00:00
Credits
Tristan Madani (@TristanInSec)
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-56123",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-26T02:03:26.743703Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-26T02:03:38.239Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "affected",
          "product": "socat",
          "repo": "https://repo.or.cz/socat.git",
          "vendor": "socat",
          "versions": [
            {
              "lessThan": "1.8.1.2",
              "status": "affected",
              "version": "1.8.0.0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Tristan Madani (@TristanInSec)"
        }
      ],
      "datePublic": "2026-06-25T00:00:00.000Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "HIGH",
            "attackRequirements": "NONE",
            "attackVector": "NETWORK",
            "baseScore": 9.2,
            "baseSeverity": "CRITICAL",
            "exploitMaturity": "NOT_DEFINED",
            "privilegesRequired": "NONE",
            "providerUrgency": "NOT_DEFINED",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "valueDensity": "NOT_DEFINED",
            "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",
            "version": "4.0",
            "vulnAvailabilityImpact": "HIGH",
            "vulnConfidentialityImpact": "HIGH",
            "vulnIntegrityImpact": "HIGH",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        },
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-122",
              "description": "Heap-based Buffer Overflow",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-25T15:43:19.580Z",
        "orgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
        "shortName": "VulnCheck"
      },
      "references": [
        {
          "tags": [
            "release-notes",
            "patch"
          ],
          "url": "http://www.dest-unreach.org/socat/CHANGES"
        },
        {
          "tags": [
            "third-party-advisory"
          ],
          "url": "https://www.vulncheck.com/advisories/socat-heap-buffer-overflow-via-socks5-reply-parser"
        }
      ],
      "source": {
        "discovery": "UNKNOWN"
      },
      "tags": [
        "x_open-source"
      ],
      "title": "socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser",
      "x_generator": {
        "engine": "vulncheck"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "83251b91-4cc7-4094-a5c7-464a1b83ea10",
    "assignerShortName": "VulnCheck",
    "cveId": "CVE-2026-56123",
    "datePublished": "2026-06-25T15:43:19.580Z",
    "dateReserved": "2026-06-18T19:15:10.651Z",
    "dateUpdated": "2026-06-26T02:03:38.239Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-56123",
      "date": "2026-06-30",
      "epss": "0.00308",
      "percentile": "0.2237"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-56123\",\"sourceIdentifier\":\"disclosure@vulncheck.com\",\"published\":\"2026-06-25T17:17:01.967\",\"lastModified\":\"2026-06-26T16:50:16.103\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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.\"}],\"affected\":[{\"source\":\"disclosure@vulncheck.com\",\"affectedData\":[{\"vendor\":\"socat\",\"product\":\"socat\",\"defaultStatus\":\"affected\",\"repo\":\"https://repo.or.cz/socat.git\",\"versions\":[{\"version\":\"1.8.0.0\",\"lessThan\":\"1.8.1.2\",\"versionType\":\"custom\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"disclosure@vulncheck.com\",\"type\":\"Secondary\",\"cvssData\":{\"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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X\",\"baseScore\":9.2,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"attackRequirements\":\"NONE\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"vulnConfidentialityImpact\":\"HIGH\",\"vulnIntegrityImpact\":\"HIGH\",\"vulnAvailabilityImpact\":\"HIGH\",\"subConfidentialityImpact\":\"NONE\",\"subIntegrityImpact\":\"NONE\",\"subAvailabilityImpact\":\"NONE\",\"exploitMaturity\":\"NOT_DEFINED\",\"confidentialityRequirement\":\"NOT_DEFINED\",\"integrityRequirement\":\"NOT_DEFINED\",\"availabilityRequirement\":\"NOT_DEFINED\",\"modifiedAttackVector\":\"NOT_DEFINED\",\"modifiedAttackComplexity\":\"NOT_DEFINED\",\"modifiedAttackRequirements\":\"NOT_DEFINED\",\"modifiedPrivilegesRequired\":\"NOT_DEFINED\",\"modifiedUserInteraction\":\"NOT_DEFINED\",\"modifiedVulnConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedVulnIntegrityImpact\":\"NOT_DEFINED\",\"modifiedVulnAvailabilityImpact\":\"NOT_DEFINED\",\"modifiedSubConfidentialityImpact\":\"NOT_DEFINED\",\"modifiedSubIntegrityImpact\":\"NOT_DEFINED\",\"modifiedSubAvailabilityImpact\":\"NOT_DEFINED\",\"Safety\":\"NOT_DEFINED\",\"Automatable\":\"NOT_DEFINED\",\"Recovery\":\"NOT_DEFINED\",\"valueDensity\":\"NOT_DEFINED\",\"vulnerabilityResponseEffort\":\"NOT_DEFINED\",\"providerUrgency\":\"NOT_DEFINED\"}}],\"cvssMetricV31\":[{\"source\":\"disclosure@vulncheck.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":8.1,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.2,\"impactScore\":5.9},{\"source\":\"nvd@nist.gov\",\"type\":\"Primary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":9.8,\"baseSeverity\":\"CRITICAL\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":5.9}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-06-26T02:03:26.743703Z\",\"id\":\"CVE-2026-56123\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"total\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"disclosure@vulncheck.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-122\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:dest-unreach:socat:*:*:*:*:*:*:*:*\",\"versionStartIncluding\":\"1.8.0.0\",\"versionEndExcluding\":\"1.8.1.2\",\"matchCriteriaId\":\"0095DC85-1977-4C52-B3EF-F8963CDF0B41\"}]}]}],\"references\":[{\"url\":\"http://www.dest-unreach.org/socat/CHANGES\",\"source\":\"disclosure@vulncheck.com\",\"tags\":[\"Release Notes\"]},{\"url\":\"https://www.vulncheck.com/advisories/socat-heap-buffer-overflow-via-socks5-reply-parser\",\"source\":\"disclosure@vulncheck.com\",\"tags\":[\"Third Party Advisory\"]}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-56123\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-06-26T02:03:26.743703Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-06-26T02:03:33.293Z\"}}], \"cna\": {\"tags\": [\"x_open-source\"], \"title\": \"socat 1.8.0.0 - 1.8.1.1 Heap Buffer Overflow via SOCKS5 Reply Parser\", \"source\": {\"discovery\": \"UNKNOWN\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"Tristan Madani (@TristanInSec)\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV4_0\": {\"Safety\": \"NOT_DEFINED\", \"version\": \"4.0\", \"Recovery\": \"NOT_DEFINED\", \"baseScore\": 9.2, \"Automatable\": \"NOT_DEFINED\", \"attackVector\": \"NETWORK\", \"baseSeverity\": \"CRITICAL\", \"valueDensity\": \"NOT_DEFINED\", \"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\", \"exploitMaturity\": \"NOT_DEFINED\", \"providerUrgency\": \"NOT_DEFINED\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"HIGH\", \"attackRequirements\": \"NONE\", \"privilegesRequired\": \"NONE\", \"subIntegrityImpact\": \"NONE\", \"vulnIntegrityImpact\": \"HIGH\", \"subAvailabilityImpact\": \"NONE\", \"vulnAvailabilityImpact\": \"HIGH\", \"subConfidentialityImpact\": \"NONE\", \"vulnConfidentialityImpact\": \"HIGH\", \"vulnerabilityResponseEffort\": \"NOT_DEFINED\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}, {\"format\": \"CVSS\", \"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 8.1, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"HIGH\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"NONE\", \"confidentialityImpact\": \"HIGH\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"repo\": \"https://repo.or.cz/socat.git\", \"vendor\": \"socat\", \"product\": \"socat\", \"versions\": [{\"status\": \"affected\", \"version\": \"1.8.0.0\", \"lessThan\": \"1.8.1.2\", \"versionType\": \"custom\"}], \"defaultStatus\": \"affected\"}], \"datePublic\": \"2026-06-25T00:00:00.000Z\", \"references\": [{\"url\": \"http://www.dest-unreach.org/socat/CHANGES\", \"tags\": [\"release-notes\", \"patch\"]}, {\"url\": \"https://www.vulncheck.com/advisories/socat-heap-buffer-overflow-via-socks5-reply-parser\", \"tags\": [\"third-party-advisory\"]}], \"x_generator\": {\"engine\": \"vulncheck\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"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.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-122\", \"description\": \"Heap-based Buffer Overflow\"}]}], \"providerMetadata\": {\"orgId\": \"83251b91-4cc7-4094-a5c7-464a1b83ea10\", \"shortName\": \"VulnCheck\", \"dateUpdated\": \"2026-06-25T15:43:19.580Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-56123\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-06-26T02:03:38.239Z\", \"dateReserved\": \"2026-06-18T19:15:10.651Z\", \"assignerOrgId\": \"83251b91-4cc7-4094-a5c7-464a1b83ea10\", \"datePublished\": \"2026-06-25T15:43:19.580Z\", \"assignerShortName\": \"VulnCheck\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.