« Back to list

CVE-2021-39246

Status: ModifiedMedium (6.1)—

Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the privacy of visits to v2 onion addresses. Exact timestamps of these onion-service visits are logged locally, and an attacker might be able to compare them to timestamp data collected by the destination server (or collected by a rogue site within the Tor network).

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).

Affected technologies (1)

Torproject — TOR Browser

CWEs

References

Raw JSON (NVD)

Show
{
  "id": "CVE-2021-39246",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 3.6,
          "accessVector": "LOCAL",
          "vectorString": "AV:L/AC:L/Au:N/C:P/I:P/A:N",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 4.9,
        "baseSeverity": "LOW",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 3.9,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 6.1,
          "attackVector": "PHYSICAL",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
          "integrityImpact": "HIGH",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.2,
        "exploitabilityScore": 0.9
      }
    ]
  },
  "affected": [
    {
      "source": "cve@mitre.org",
      "affectedData": [
        {
          "vendor": "n/a",
          "product": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-09-24T19:15:07.147",
  "references": [
    {
      "url": "https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-111.md",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://gitlab.torproject.org/tpo/core/tor/-/commit/80c404c4b79f3bcba3fc4585d4c62a62a04f3ed9",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://gitlab.torproject.org/tpo/core/tor/-/merge_requests/434",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://sick.codes/sick-2021-111",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://www.privacyaffairs.com/cve-2021-39246-tor-vulnerability",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "cve@mitre.org"
    },
    {
      "url": "https://github.com/sickcodes/security/blob/master/advisories/SICK-2021-111.md",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://gitlab.torproject.org/tpo/core/tor/-/commit/80c404c4b79f3bcba3fc4585d4c62a62a04f3ed9",
      "tags": [
        "Patch",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://gitlab.torproject.org/tpo/core/tor/-/merge_requests/434",
      "tags": [
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://sick.codes/sick-2021-111",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.privacyaffairs.com/cve-2021-39246-tor-vulnerability",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-532"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Tor Browser through 10.5.6 and 11.x through 11.0a4 allows a correlation attack that can compromise the privacy of visits to v2 onion addresses. Exact timestamps of these onion-service visits are logged locally, and an attacker might be able to compare them to timestamp data collected by the destination server (or collected by a rogue site within the Tor network)."
    },
    {
      "lang": "es",
      "value": "Tor Browser hasta la versión 10.5.6 y la versión 11.x hasta la 11.0a4 permite un ataque de correlación que puede comprometer la privacidad de las visitas a las direcciones v2 de la cebolla. Las marcas de tiempo exactas de estas visitas al servicio de cebolla se registran localmente, y un atacante podría ser capaz de compararlas con los datos de las marcas de tiempo recogidas por el servidor de destino (o recogidas por un sitio falso dentro de la red Tor)"
    }
  ],
  "lastModified": "2026-06-17T04:03:23.677",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:torproject:tor_browser:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "E2A501C7-B8B3-4E18-9538-25DEDF2A644F",
              "versionEndIncluding": "10.5.6"
            },
            {
              "criteria": "cpe:2.3:a:torproject:tor_browser:11.0:alpha2:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "45031E29-6854-481E-9D53-5D2EACF3BA03"
            },
            {
              "criteria": "cpe:2.3:a:torproject:tor_browser:11.0:alpha4:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "48C405F5-103C-4FE3-A066-DE1BE00CDC7D"
            }
          ],
          "operator": "OR"
        },
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:o:apple:macos:-:*:*:*:*:*:*:*",
              "vulnerable": false,
              "matchCriteriaId": "387021A0-AF36-463C-A605-32EA7DAC172E"
            },
            {
              "criteria": "cpe:2.3:o:linux:linux_kernel:-:*:*:*:*:*:*:*",
              "vulnerable": false,
              "matchCriteriaId": "703AF700-7A70-47E2-BC3A-7FD03B3CA9C1"
            },
            {
              "criteria": "cpe:2.3:o:microsoft:windows:-:*:*:*:*:*:*:*",
              "vulnerable": false,
              "matchCriteriaId": "A2572D17-1DE6-457B-99CC-64AFD54487EA"
            }
          ],
          "operator": "OR"
        }
      ],
      "operator": "AND"
    }
  ],
  "sourceIdentifier": "cve@mitre.org"
}