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CVE-2026-5501

Status: AnalyzedHigh (8.6)—

wolfSSL_X509_verify_cert in the OpenSSL compatibility layer accepts a certificate chain in which the leaf's signature is not checked, if the attacker supplies an untrusted intermediate with Basic Constraints `CA:FALSE` that is legitimately signed by a trusted root. An attacker who obtains any leaf certificate from a trusted CA (e.g. a free DV cert from Let's Encrypt) can forge a certificate for any subject name with any public key and arbitrary signature bytes, and the function returns `WOLFSSL_SUCCESS` / `X509_V_OK`. The native wolfSSL TLS handshake path (`ProcessPeerCerts`) is not susceptible and the issue is limited to applications using the OpenSSL compatibility API directly, which would include integrations of wolfSSL into nginx and haproxy.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

Acceso en red con PR:L requiere comunicación con servicio remoto (verificación de certificados en TLS). La cadena de certificados forjada permite MITM fraudulento. Confianza alta por detalles técnicos explícitos del CWE-295.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Disable or Remove Feature or ProgramVulnerability ScanningUser TrainingThreat Intelligence ProgramPrivileged Account ManagementNetwork Segmentation

Affected technologies (1)

Wolfssl — Wolfssl

CWEs

References

Raw JSON (NVD)

Show
{
  "id": "CVE-2026-5501",
  "cveTags": [],
  "metrics": {
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      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-5501",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "total"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-04-22T03:55:48.544190Z"
        }
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    ],
    "cvssMetricV31": [
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        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
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          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
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    ],
    "cvssMetricV40": [
      {
        "type": "Secondary",
        "source": "facts@wolfssl.com",
        "cvssData": {
          "Safety": "NOT_DEFINED",
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          "Automatable": "NOT_DEFINED",
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          "baseSeverity": "HIGH",
          "valueDensity": "NOT_DEFINED",
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          "confidentialityRequirement": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "vulnerabilityResponseEffort": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED"
        }
      }
    ]
  },
  "affected": [
    {
      "source": "facts@wolfssl.com",
      "affectedData": [
        {
          "vendor": "wolfSSL",
          "modules": [
            "wolfSSL_X509_verify_cert"
          ],
          "product": "wolfSSL",
          "versions": [
            {
              "status": "affected",
              "version": "0",
              "versionType": "semver",
              "lessThanOrEqual": "5.9.0"
            }
          ],
          "programFiles": [
            "src/x509_str.c"
          ],
          "defaultStatus": "unaffected"
        }
      ]
    }
  ],
  "published": "2026-04-10T04:17:17.230",
  "references": [
    {
      "url": "https://github.com/wolfSSL/wolfssl/pull/10102",
      "tags": [
        "Issue Tracking"
      ],
      "source": "facts@wolfssl.com"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "facts@wolfssl.com",
      "description": [
        {
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          "value": "CWE-295"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "wolfSSL_X509_verify_cert in the OpenSSL compatibility layer accepts a certificate chain in which the leaf's signature is not checked, if the attacker supplies an untrusted intermediate with Basic Constraints `CA:FALSE` that is legitimately signed by a trusted root. An attacker who obtains any leaf certificate from a trusted CA (e.g. a free DV cert from Let's Encrypt) can forge a certificate for any subject name with any public key and arbitrary signature bytes, and the function returns `WOLFSSL_SUCCESS` / `X509_V_OK`. The native wolfSSL TLS handshake path (`ProcessPeerCerts`) is not susceptible and the issue is limited to applications using the OpenSSL compatibility API directly, which would include integrations of wolfSSL into nginx and haproxy."
    }
  ],
  "lastModified": "2026-06-17T10:59:07.810",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "vulnerable": true,
              "matchCriteriaId": "DA5C710C-46E8-470C-83AF-D33D1A40512D",
              "versionEndIncluding": "5.9.0"
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          ],
          "operator": "OR"
        }
      ]
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  ],
  "sourceIdentifier": "facts@wolfssl.com"
}