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CVE-2026-50721

Estado: AnalizadaMedia (5.9)—

Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. A remote attacker can use a variation on the Bleichenbacher attack to forge the SIG payload when small public exponents are being used (e.g., e=3), which could lead to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the SIG payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of remote IKE peers are not affected.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Libreswan — Libreswan

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-50721",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-50721",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "yes"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-07-06T18:12:17.199605Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "d42dc95b-23f1-4e06-9076-20753a0fb0df",
        "cvssData": {
          "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"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 2.2
      },
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.9,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 2.2
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  "affected": [
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      "source": "d42dc95b-23f1-4e06-9076-20753a0fb0df",
      "affectedData": [
        {
          "repo": "https://github.com/libreswan/libreswan",
          "vendor": "The Libreswan Project",
          "product": "libreswan",
          "versions": [
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              "status": "affected",
              "version": "0",
              "versionType": "semver",
              "lessThanOrEqual": "5.3"
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              "version": "5.3.1",
              "versionType": "semver"
            }
          ],
          "packageName": "libreswan",
          "collectionURL": "https://github.com/libreswan/libreswan",
          "defaultStatus": "unaffected",
          "programRoutines": [
            {
              "name": "RSA_authenticate_hash_signature_raw_rsa"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-07-02T22:16:43.367",
  "references": [
    {
      "url": "https://libreswan.org/security/CVE-2026-50721/",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "d42dc95b-23f1-4e06-9076-20753a0fb0df"
    },
    {
      "url": "https://libreswan.org/security/CVE-2026-50721/CVE-2026-50721.txt",
      "tags": [
        "Vendor Advisory"
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      "source": "d42dc95b-23f1-4e06-9076-20753a0fb0df"
    },
    {
      "url": "https://libreswan.org/security/CVE-2026-50722/CVE-2026-50722.txt",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "d42dc95b-23f1-4e06-9076-20753a0fb0df"
    },
    {
      "url": "https://www.rfc-editor.org/rfc/rfc2313",
      "tags": [
        "Technical Description"
      ],
      "source": "d42dc95b-23f1-4e06-9076-20753a0fb0df"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "d42dc95b-23f1-4e06-9076-20753a0fb0df",
      "description": [
        {
          "lang": "en",
          "value": "CWE-347"
        },
        {
          "lang": "en",
          "value": "CWE-617"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Libreswan, via the function RSA_authenticate_hash_signature_raw_rsa(), did not correctly verify the length of the authentication hash when the SIG payload of an IKEv1 packet was encoded using PKCS #1 RSA Encryption as per RFC 2313. A remote attacker can use a variation on the Bleichenbacher attack to forge the SIG payload when small public exponents are being used (e.g., e=3), which could lead to impersonation. Additionally, a remote attacker, by encoding a shorter than expected hash in the SIG payload, could trigger an assertion leading to denial-of-service. The daemon aborts and restarts; continued exploitation causes sustained denial of service. Remote code execution is not possible. X.509 certificate verifications of remote IKE peers are not affected."
    }
  ],
  "lastModified": "2026-07-09T15:46:40.770",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:libreswan:libreswan:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "0D5C4D8F-3003-4ACA-A065-E03AEE680115",
              "versionEndExcluding": "5.3.1"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "d42dc95b-23f1-4e06-9076-20753a0fb0df"
}