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CVE-2021-29967

Status: ModifiedHigh (8.8)—

Mozilla developers reported memory safety bugs present in Firefox 88 and Firefox ESR 78.11. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Thunderbird < 78.11, Firefox < 89, and Firefox ESR < 78.11.

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 (3)

Mozilla — FirefoxMozilla — Firefox ESRMozilla — Thunderbird

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2021-29967",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 6.8,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:M/Au:N/C:P/I:P/A:P",
          "authentication": "NONE",
          "integrityImpact": "PARTIAL",
          "accessComplexity": "MEDIUM",
          "availabilityImpact": "PARTIAL",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 6.4,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8.6,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": true
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 8.8,
          "attackVector": "NETWORK",
          "baseSeverity": "HIGH",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
          "integrityImpact": "HIGH",
          "userInteraction": "REQUIRED",
          "attackComplexity": "LOW",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 5.9,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "security@mozilla.org",
      "affectedData": [
        {
          "vendor": "Mozilla",
          "product": "Thunderbird",
          "versions": [
            {
              "status": "affected",
              "version": "unspecified",
              "lessThan": "78.11",
              "versionType": "custom"
            }
          ]
        },
        {
          "vendor": "Mozilla",
          "product": "Firefox",
          "versions": [
            {
              "status": "affected",
              "version": "unspecified",
              "lessThan": "89",
              "versionType": "custom"
            }
          ]
        },
        {
          "vendor": "Mozilla",
          "product": "Firefox ESR",
          "versions": [
            {
              "status": "affected",
              "version": "unspecified",
              "lessThan": "78.11",
              "versionType": "custom"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-06-24T14:15:10.423",
  "references": [
    {
      "url": "https://bugzilla.mozilla.org/buglist.cgi?bug_id=1602862%2C1703191%2C1703760%2C1704722%2C1706041",
      "tags": [
        "Issue Tracking",
        "Not Applicable",
        "Third Party Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://security.gentoo.org/glsa/202208-14",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2021-23/",
      "tags": [
        "Release Notes",
        "Vendor Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2021-24/",
      "tags": [
        "Release Notes",
        "Vendor Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2021-26/",
      "tags": [
        "Release Notes",
        "Vendor Advisory"
      ],
      "source": "security@mozilla.org"
    },
    {
      "url": "https://bugzilla.mozilla.org/buglist.cgi?bug_id=1602862%2C1703191%2C1703760%2C1704722%2C1706041",
      "tags": [
        "Issue Tracking",
        "Not Applicable",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://security.gentoo.org/glsa/202208-14",
      "tags": [
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2021-23/",
      "tags": [
        "Release Notes",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2021-24/",
      "tags": [
        "Release Notes",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://www.mozilla.org/security/advisories/mfsa2021-26/",
      "tags": [
        "Release Notes",
        "Vendor Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-787"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "Mozilla developers reported memory safety bugs present in Firefox 88 and Firefox ESR 78.11. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Thunderbird < 78.11, Firefox < 89, and Firefox ESR < 78.11."
    },
    {
      "lang": "es",
      "value": "Los desarrolladores de Mozilla han reportado bugs de seguridad de memoria presentes en Firefox versión 88 y Firefox ESR versión 78.11. Algunos de estos bugs mostraban evidencias de corrupción de memoria y presumimos que con el suficiente esfuerzo algunos de ellos podrían haber sido explotados para ejecutar código arbitrario. Esta vulnerabilidad afecta a Thunderbird versiones anteriores a 78.11, Firefox versiones anteriores a 89 y Firefox ESR versiones anteriores a 78.11"
    }
  ],
  "lastModified": "2026-06-17T03:48:31.573",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
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              "vulnerable": true,
              "matchCriteriaId": "649A8514-B864-450C-9FE0-0FA48641CFEB",
              "versionEndExcluding": "89.0"
            },
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              "vulnerable": true,
              "matchCriteriaId": "F803E821-2329-4FDA-B110-EEC8EDB632DD",
              "versionEndExcluding": "78.11"
            },
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          "operator": "OR"
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  ],
  "sourceIdentifier": "security@mozilla.org"
}