Vulnerability-Lookup

UBUNTU-CVE-2021-36647 (CVE-2021-36647)

Vulnerability from osv_ubuntu – Published: 2023-01-17 21:15 – Updated: 2026-04-22 07:40 – Source website

Details

Use of a Broken or Risky Cryptographic Algorithm in the function mbedtls_mpi_exp_mod() in lignum.c in Mbed TLS Mbed TLS all versions before 3.0.0, 2.27.0 or 2.16.11 allows attackers with access to precise enough timing and memory access information (typically an untrusted operating system attacking a secure enclave such as SGX or the TrustZone secure world) to recover the private keys used in RSA.

Severity

4.7 (Medium)


                    
                      CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

4.7 (Medium)


                    
                      CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

N/A (UNKNOWN)


                    
                      medium

References

URL

Type

	https://ubuntu.com/security/CVE-2021-36647	REPORT
	https://kouzili.com/Load-Step.pdf	REPORT
	https://tls.mbed.org/tech-updates/security-adviso…	REPORT
	https://github.com/ARMmbed/mbedtls/releases/	REPORT
	https://www.cve.org/CVERecord?id=CVE-2021-36647	REPORT

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libmbedcrypto0",
            "binary_version": "2.2.1-2ubuntu0.3"
          },
          {
            "binary_name": "libmbedtls10",
            "binary_version": "2.2.1-2ubuntu0.3"
          },
          {
            "binary_name": "libmbedx509-0",
            "binary_version": "2.2.1-2ubuntu0.3"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:16.04:LTS",
        "name": "mbedtls",
        "purl": "pkg:deb/ubuntu/mbedtls@2.2.1-2ubuntu0.3?arch=source\u0026distro=xenial"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.1.2-1",
        "2.2.0-1",
        "2.2.1-1",
        "2.2.1-2",
        "2.2.1-2ubuntu0.1",
        "2.2.1-2ubuntu0.2",
        "2.2.1-2ubuntu0.3"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libmbedcrypto1",
            "binary_version": "2.8.0-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libmbedtls10",
            "binary_version": "2.8.0-1ubuntu0.1~esm1"
          },
          {
            "binary_name": "libmbedx509-0",
            "binary_version": "2.8.0-1ubuntu0.1~esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:18.04:LTS",
        "name": "mbedtls",
        "purl": "pkg:deb/ubuntu/mbedtls@2.8.0-1ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/bionic"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.5.1-1ubuntu1",
        "2.6.0-1",
        "2.7.0-2",
        "2.8.0-1",
        "2.8.0-1ubuntu0.1~esm1"
      ]
    },
    {
      "ecosystem_specific": {
        "binaries": [
          {
            "binary_name": "libmbedcrypto3",
            "binary_version": "2.16.4-1ubuntu2+esm1"
          },
          {
            "binary_name": "libmbedtls12",
            "binary_version": "2.16.4-1ubuntu2+esm1"
          },
          {
            "binary_name": "libmbedx509-0",
            "binary_version": "2.16.4-1ubuntu2+esm1"
          }
        ]
      },
      "package": {
        "ecosystem": "Ubuntu:Pro:20.04:LTS",
        "name": "mbedtls",
        "purl": "pkg:deb/ubuntu/mbedtls@2.16.4-1ubuntu2+esm1?arch=source\u0026distro=esm-apps/focal"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.16.2-1",
        "2.16.3-1",
        "2.16.4-1ubuntu2",
        "2.16.4-1ubuntu2+esm1"
      ]
    }
  ],
  "aliases": [],
  "details": "Use of a Broken or Risky Cryptographic Algorithm in the function mbedtls_mpi_exp_mod() in lignum.c in Mbed TLS Mbed TLS all versions before 3.0.0, 2.27.0 or 2.16.11 allows attackers with access to precise enough timing and memory access information (typically an untrusted operating system attacking a secure enclave such as SGX or the TrustZone secure world) to recover the private keys used in RSA.",
  "id": "UBUNTU-CVE-2021-36647",
  "modified": "2026-04-22T07:40:06Z",
  "published": "2023-01-17T21:15:00Z",
  "references": [
    {
      "type": "REPORT",
      "url": "https://ubuntu.com/security/CVE-2021-36647"
    },
    {
      "type": "REPORT",
      "url": "https://kouzili.com/Load-Step.pdf"
    },
    {
      "type": "REPORT",
      "url": "https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1"
    },
    {
      "type": "REPORT",
      "url": "https://github.com/ARMmbed/mbedtls/releases/"
    },
    {
      "type": "REPORT",
      "url": "https://www.cve.org/CVERecord?id=CVE-2021-36647"
    }
  ],
  "related": [],
  "schema_version": "1.7.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "medium",
      "type": "Ubuntu"
    }
  ],
  "upstream": [
    "CVE-2021-36647"
  ]
}

CVE-2021-36647 (GCVE-0-2021-36647)

Vulnerability from cvelistv5 – Published: 2023-01-17 00:00 – Updated: 2025-11-03 19:26

Summary

Severity

4.7 (Medium)


                        
                          CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2025-04-08 20:30 UTC

CWE

n/a
CWE-327 - Use of a Broken or Risky Cryptographic Algorithm

Assigner

mitre mitre root

References

4 references

URL	Tags
https://kouzili.com/Load-Step.pdf
https://github.com/ARMmbed/mbedtls/releases/
https://tls.mbed.org/tech-updates/security-adviso…
https://lists.debian.org/debian-lts-announce/2025…

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2025-11-03T19:26:11.739Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://kouzili.com/Load-Step.pdf"
          },
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://github.com/ARMmbed/mbedtls/releases/"
          },
          {
            "tags": [
              "x_transferred"
            ],
            "url": "https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1"
          },
          {
            "url": "https://lists.debian.org/debian-lts-announce/2025/06/msg00034.html"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "cvssV3_1": {
              "attackComplexity": "HIGH",
              "attackVector": "LOCAL",
              "availabilityImpact": "NONE",
              "baseScore": 4.7,
              "baseSeverity": "MEDIUM",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "NONE",
              "privilegesRequired": "LOW",
              "scope": "UNCHANGED",
              "userInteraction": "NONE",
              "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N",
              "version": "3.1"
            }
          },
          {
            "other": {
              "content": {
                "id": "CVE-2021-36647",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2025-04-08T20:30:16.965859Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-327",
                "description": "CWE-327 Use of a Broken or Risky Cryptographic Algorithm",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2025-04-08T20:31:32.007Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "n/a",
          "vendor": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Use of a Broken or Risky Cryptographic Algorithm in the function mbedtls_mpi_exp_mod() in lignum.c in Mbed TLS Mbed TLS all versions before 3.0.0, 2.27.0 or 2.16.11 allows attackers with access to precise enough timing and memory access information (typically an untrusted operating system attacking a secure enclave such as SGX or the TrustZone secure world) to recover the private keys used in RSA."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "n/a",
              "lang": "en",
              "type": "text"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2023-01-17T00:00:00.000Z",
        "orgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca",
        "shortName": "mitre"
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      "references": [
        {
          "url": "https://kouzili.com/Load-Step.pdf"
        },
        {
          "url": "https://github.com/ARMmbed/mbedtls/releases/"
        },
        {
          "url": "https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1"
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca",
    "assignerShortName": "mitre",
    "cveId": "CVE-2021-36647",
    "datePublished": "2023-01-17T00:00:00.000Z",
    "dateReserved": "2021-07-12T00:00:00.000Z",
    "dateUpdated": "2025-11-03T19:26:11.739Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

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UBUNTU-CVE-2021-36647 (CVE-2021-36647)

CVE-2021-36647 (GCVE-0-2021-36647)

Tags

Sightings

Nomenclature

Related by attack behaviour