{
  "cvss": 9.2,
  "datePublished": "2026-06-17T20:17:28.667",
  "dateUpdated": "2026-10-22T19:17:55.937",
  "description": "libssh2 1.11.1, fixed in commit 97acf3d, contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution.",
  "id": "CVE-2026-55200",
  "raw": {
    "affected": [
      {
        "affectedData": [
          {
            "defaultStatus": "unaffected",
            "packageURL": "pkg:github/libssh2/libssh2",
            "product": "libssh2",
            "repo": "https://github.com/libssh2/libssh2",
            "vendor": "libssh2",
            "versions": [
              {
                "status": "affected",
                "version": "1.11.1",
                "versionType": "semver"
              },
              {
                "lessThan": "97acf3dfda80c91c3a8c9f2372546301d4a1a7a8",
                "status": "affected",
                "version": "1c3f1b7da588f2652260285529ec3c1f1125eb4e",
                "versionType": "git"
              }
            ]
          }
        ],
        "source": "disclosure@vulncheck.com"
      }
    ],
    "configurations": [
      {
        "nodes": [
          {
            "cpeMatch": [
              {
                "criteria": "cpe:2.3:a:libssh2:libssh2:1.11.1:*:*:*:*:*:*:*",
                "matchCriteriaId": "B190FBC9-6216-4759-BEF0-747B01BBD92B",
                "vulnerable": true
              }
            ],
            "negate": false,
            "operator": "OR"
          }
        ]
      }
    ],
    "cveTags": [],
    "descriptions": [
      {
        "lang": "en",
        "value": "libssh2 1.11.1, fixed in commit 97acf3d, contains an out-of-bounds write vulnerability in ssh2_transport_read() that fails to enforce upper bounds on packet_length field. Remote attackers can send crafted SSH packets with excessively large packet_length values to corrupt heap memory and achieve remote code execution."
      }
    ],
    "id": "CVE-2026-55200",
    "lastModified": "2026-10-22T19:17:55.937",
    "metrics": {
      "cvssMetricV31": [
        {
          "cvssData": {
            "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"
          },
          "exploitabilityScore": 2.2,
          "impactScore": 5.9,
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          "type": "Secondary"
        },
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          "cvssData": {
            "attackComplexity": "LOW",
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            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
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            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:L",
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        }
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      "cvssMetricV40": [
        {
          "cvssData": {
            "Automatable": "NOT_DEFINED",
            "Recovery": "NOT_DEFINED",
            "Safety": "NOT_DEFINED",
            "attackComplexity": "LOW",
            "attackRequirements": "PRESENT",
            "attackVector": "NETWORK",
            "availabilityRequirement": "NOT_DEFINED",
            "baseScore": 9.2,
            "baseSeverity": "CRITICAL",
            "confidentialityRequirement": "NOT_DEFINED",
            "exploitMaturity": "NOT_DEFINED",
            "integrityRequirement": "NOT_DEFINED",
            "modifiedAttackComplexity": "NOT_DEFINED",
            "modifiedAttackRequirements": "NOT_DEFINED",
            "modifiedAttackVector": "NOT_DEFINED",
            "modifiedPrivilegesRequired": "NOT_DEFINED",
            "modifiedSubAvailabilityImpact": "NOT_DEFINED",
            "modifiedSubConfidentialityImpact": "NOT_DEFINED",
            "modifiedSubIntegrityImpact": "NOT_DEFINED",
            "modifiedUserInteraction": "NOT_DEFINED",
            "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
            "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
            "modifiedVulnIntegrityImpact": "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:L/AT:P/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",
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            "vulnIntegrityImpact": "HIGH",
            "vulnerabilityResponseEffort": "NOT_DEFINED"
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            "options": [
              {
                "exploitation": "poc"
              },
              {
                "automatable": "no"
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              {
                "technicalImpact": "total"
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            "role": "CISA Coordinator",
            "timestamp": "2026-06-17T00:00:00+00:00",
            "version": "2.0.3"
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    "published": "2026-06-17T20:17:28.667",
    "references": [
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Patch"
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        "url": "https://github.com/libssh2/libssh2/commit/97acf3dfda80c91c3a8c9f2372546301d4a1a7a8"
      },
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        "url": "https://github.com/libssh2/libssh2/pull/2052"
      },
      {
        "source": "disclosure@vulncheck.com",
        "tags": [
          "Third Party Advisory"
        ],
        "url": "https://www.vulncheck.com/advisories/libssh2-out-of-bounds-write-via-unchecked-packet-length-in-transport-c"
      },
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        "url": "https://web.archive.org/web/20260623211210/https://github.com/bikini/exploitarium/tree/main/libssh2-cve-2026-55200-poc"
      }
    ],
    "sourceIdentifier": "disclosure@vulncheck.com",
    "vulnStatus": "Modified",
    "weaknesses": [
      {
        "description": [
          {
            "lang": "en",
            "value": "CWE-680"
          }
        ],
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ]
  },
  "severity": "CRITICAL",
  "source": "nvd",
  "title": "libssh2 1.11.1, fixed in commit 97acf3d, contains an out-of-bounds write vulnerability in ssh2_transport_read() that ..."
}