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CVE-2016-20013

Status: ModifiedHigh (7.5)—
Severity7.5High · CVSS 3.1
Exploitation probability2.17 %higher than 82% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitNot knownno public code found

sha256crypt and sha512crypt through 0.6 allow attackers to cause a denial of service (CPU consumption) because the algorithm's runtime is proportional to the square of the length of the password.

CVSS

Base score
7.5
Version
3.1
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days
2.17 %
Percentile among all scored CVEs
82
Score date
10/24/2026

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).

Affected technologies (2)

Sha256crypt Project — Sha256cryptSha512crypt Project — Sha512crypt

CWEs

References

Show 6 references

Raw JSON (NVD)

Show
{
  "id": "CVE-2016-20013",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 5,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:N/C:N/I:N/A:P",
          "authentication": "NONE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "NONE"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 10,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 7.5,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ]
    }
  ],
  "published": "2022-02-19T05:15:09.413",
  "references": [
    {
      "url": "https://akkadia.org/drepper/SHA-crypt.txt",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://pthree.org/2018/05/23/do-not-use-sha256crypt-sha512crypt-theyre-dangerous/",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://twitter.com/solardiz/status/795601240151457793",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://akkadia.org/drepper/SHA-crypt.txt",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://pthree.org/2018/05/23/do-not-use-sha256crypt-sha512crypt-theyre-dangerous/",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://twitter.com/solardiz/status/795601240151457793",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-770"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "sha256crypt and sha512crypt through 0.6 allow attackers to cause a denial of service (CPU consumption) because the algorithm's runtime is proportional to the square of the length of the password."
    },
    {
      "lang": "es",
      "value": "sha256crypt y sha512crypt versiones hasta 0.6, permiten a atacantes causar una denegación de servicio (consumo de CPU) porque el tiempo de ejecución del algoritmo es proporcional al cuadrado de la longitud de la contraseña"
    }
  ],
  "lastModified": "2026-06-17T00:43:05.270",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:sha256crypt_project:sha256crypt:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "1697E25C-6F31-4976-BC6A-82447C6DF44E",
              "versionEndIncluding": "0.6"
            },
            {
              "criteria": "cpe:2.3:a:sha512crypt_project:sha512crypt:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "91C2A358-8551-4E21-BF7C-47D00524D451",
              "versionEndIncluding": "0.6"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "cve@mitre.org"
}