GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

CVE-2020-26950 (GCVE-0-2020-26950)

Vulnerability from cvelistv5 – Published: 2020-12-09 00:19 – Updated: 2024-08-04 16:03
VLAI
Summary
In certain circumstances, the MCallGetProperty opcode can be emitted with unmet assumptions resulting in an exploitable use-after-free condition. This vulnerability affects Firefox < 82.0.3, Firefox ESR < 78.4.1, and Thunderbird < 78.4.2.
CWE
  • Write side effects in MCallGetProperty opcode not accounted for
Impacted products
Vendor Product Version CPE status
Mozilla Firefox Affected: < 82.0.3
guessed Create a notification for this product.
Mozilla Firefox ESR Affected: < 78.4.1
guessed Create a notification for this product.
Mozilla Thunderbird Affected: < 78.4.2
guessed Create a notification for this product.
Show details on NVD website

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2024-08-04T16:03:22.903Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "tags": [
              "x_refsource_MISC",
              "x_transferred"
            ],
            "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1675905"
          },
          {
            "tags": [
              "x_refsource_CONFIRM",
              "x_transferred"
            ],
            "url": "https://www.mozilla.org/security/advisories/mfsa2020-49/"
          },
          {
            "tags": [
              "x_refsource_MISC",
              "x_transferred"
            ],
            "url": "http://packetstormsecurity.com/files/166175/Firefox-MCallGetProperty-Write-Side-Effects-Use-After-Free.html"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "Firefox",
          "vendor": "Mozilla",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 82.0.3"
            }
          ]
        },
        {
          "product": "Firefox ESR",
          "vendor": "Mozilla",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 78.4.1"
            }
          ]
        },
        {
          "product": "Thunderbird",
          "vendor": "Mozilla",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 78.4.2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In certain circumstances, the MCallGetProperty opcode can be emitted with unmet assumptions resulting in an exploitable use-after-free condition. This vulnerability affects Firefox \u003c 82.0.3, Firefox ESR \u003c 78.4.1, and Thunderbird \u003c 78.4.2."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "Write side effects in MCallGetProperty opcode not accounted for",
              "lang": "en",
              "type": "text"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2022-03-01T17:06:11.000Z",
        "orgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe",
        "shortName": "mozilla"
      },
      "references": [
        {
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1675905"
        },
        {
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://www.mozilla.org/security/advisories/mfsa2020-49/"
        },
        {
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "http://packetstormsecurity.com/files/166175/Firefox-MCallGetProperty-Write-Side-Effects-Use-After-Free.html"
        }
      ],
      "x_legacyV4Record": {
        "CVE_data_meta": {
          "ASSIGNER": "security@mozilla.org",
          "ID": "CVE-2020-26950",
          "STATE": "PUBLIC"
        },
        "affects": {
          "vendor": {
            "vendor_data": [
              {
                "product": {
                  "product_data": [
                    {
                      "product_name": "Firefox",
                      "version": {
                        "version_data": [
                          {
                            "version_value": "\u003c 82.0.3"
                          }
                        ]
                      }
                    },
                    {
                      "product_name": "Firefox ESR",
                      "version": {
                        "version_data": [
                          {
                            "version_value": "\u003c 78.4.1"
                          }
                        ]
                      }
                    },
                    {
                      "product_name": "Thunderbird",
                      "version": {
                        "version_data": [
                          {
                            "version_value": "\u003c 78.4.2"
                          }
                        ]
                      }
                    }
                  ]
                },
                "vendor_name": "Mozilla"
              }
            ]
          }
        },
        "data_format": "MITRE",
        "data_type": "CVE",
        "data_version": "4.0",
        "description": {
          "description_data": [
            {
              "lang": "eng",
              "value": "In certain circumstances, the MCallGetProperty opcode can be emitted with unmet assumptions resulting in an exploitable use-after-free condition. This vulnerability affects Firefox \u003c 82.0.3, Firefox ESR \u003c 78.4.1, and Thunderbird \u003c 78.4.2."
            }
          ]
        },
        "problemtype": {
          "problemtype_data": [
            {
              "description": [
                {
                  "lang": "eng",
                  "value": "Write side effects in MCallGetProperty opcode not accounted for"
                }
              ]
            }
          ]
        },
        "references": {
          "reference_data": [
            {
              "name": "https://bugzilla.mozilla.org/show_bug.cgi?id=1675905",
              "refsource": "MISC",
              "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1675905"
            },
            {
              "name": "https://www.mozilla.org/security/advisories/mfsa2020-49/",
              "refsource": "CONFIRM",
              "url": "https://www.mozilla.org/security/advisories/mfsa2020-49/"
            },
            {
              "name": "http://packetstormsecurity.com/files/166175/Firefox-MCallGetProperty-Write-Side-Effects-Use-After-Free.html",
              "refsource": "MISC",
              "url": "http://packetstormsecurity.com/files/166175/Firefox-MCallGetProperty-Write-Side-Effects-Use-After-Free.html"
            }
          ]
        }
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "f16b083a-5664-49f3-a51e-8d479e5ed7fe",
    "assignerShortName": "mozilla",
    "cveId": "CVE-2020-26950",
    "datePublished": "2020-12-09T00:19:22.000Z",
    "dateReserved": "2020-10-12T00:00:00.000Z",
    "dateUpdated": "2024-08-04T16:03:22.903Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2020-26950",
      "date": "2026-09-19",
      "epss": "0.42327",
      "percentile": "0.98637"
    },
    "fkie_nvd": {
      "configurations": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*",
                  "matchCriteriaId": "7F743C78-6F4E-4BD7-A878-B887A2C42BDC",
                  "versionEndExcluding": "82.0.3",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*",
                  "matchCriteriaId": "08D6779A-1193-446D-AE3E-D859D539A170",
                  "versionEndExcluding": "78.4.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*",
                  "matchCriteriaId": "635C87C4-E16B-4320-A339-45C8E1DF0401",
                  "versionEndExcluding": "78.4.2",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In certain circumstances, the MCallGetProperty opcode can be emitted with unmet assumptions resulting in an exploitable use-after-free condition. This vulnerability affects Firefox \u003c 82.0.3, Firefox ESR \u003c 78.4.1, and Thunderbird \u003c 78.4.2."
        },
        {
          "lang": "es",
          "value": "En determinadas circunstancias, el opcode MCallGetProperty puede ser emitido con suposiciones no cumplidas, resultando en una condici\u00f3n de uso de la memoria previamente liberada explotable. Esta vulnerabilidad afecta a Firefox versiones anteriores a 82.0.3, Firefox ESR versiones anteriores a 78.4.1, y Thunderbird versiones anteriores a 78.4.2"
        }
      ],
      "id": "CVE-2020-26950",
      "lastModified": "2024-11-21T05:20:33.823",
      "metrics": {
        "cvssMetricV2": [
          {
            "acInsufInfo": false,
            "baseSeverity": "HIGH",
            "cvssData": {
              "accessComplexity": "MEDIUM",
              "accessVector": "NETWORK",
              "authentication": "NONE",
              "availabilityImpact": "COMPLETE",
              "baseScore": 9.3,
              "confidentialityImpact": "COMPLETE",
              "integrityImpact": "COMPLETE",
              "vectorString": "AV:N/AC:M/Au:N/C:C/I:C/A:C",
              "version": "2.0"
            },
            "exploitabilityScore": 8.6,
            "impactScore": 10.0,
            "obtainAllPrivilege": false,
            "obtainOtherPrivilege": false,
            "obtainUserPrivilege": false,
            "source": "nvd@nist.gov",
            "type": "Primary",
            "userInteractionRequired": true
          }
        ],
        "cvssMetricV31": [
          {
            "cvssData": {
              "attackComplexity": "LOW",
              "attackVector": "NETWORK",
              "availabilityImpact": "HIGH",
              "baseScore": 8.8,
              "baseSeverity": "HIGH",
              "confidentialityImpact": "HIGH",
              "integrityImpact": "HIGH",
              "privilegesRequired": "NONE",
              "scope": "UNCHANGED",
              "userInteraction": "REQUIRED",
              "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
              "version": "3.1"
            },
            "exploitabilityScore": 2.8,
            "impactScore": 5.9,
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      },
      "published": "2020-12-09T01:15:12.503",
      "references": [
        {
          "source": "security@mozilla.org",
          "tags": [
            "Exploit",
            "Third Party Advisory",
            "VDB Entry"
          ],
          "url": "http://packetstormsecurity.com/files/166175/Firefox-MCallGetProperty-Write-Side-Effects-Use-After-Free.html"
        },
        {
          "source": "security@mozilla.org",
          "tags": [
            "Exploit",
            "Issue Tracking",
            "Vendor Advisory"
          ],
          "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1675905"
        },
        {
          "source": "security@mozilla.org",
          "tags": [
            "Vendor Advisory"
          ],
          "url": "https://www.mozilla.org/security/advisories/mfsa2020-49/"
        },
        {
          "source": "af854a3a-2127-422b-91ae-364da2661108",
          "tags": [
            "Exploit",
            "Third Party Advisory",
            "VDB Entry"
          ],
          "url": "http://packetstormsecurity.com/files/166175/Firefox-MCallGetProperty-Write-Side-Effects-Use-After-Free.html"
        },
        {
          "source": "af854a3a-2127-422b-91ae-364da2661108",
          "tags": [
            "Exploit",
            "Issue Tracking",
            "Vendor Advisory"
          ],
          "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1675905"
        },
        {
          "source": "af854a3a-2127-422b-91ae-364da2661108",
          "tags": [
            "Vendor Advisory"
          ],
          "url": "https://www.mozilla.org/security/advisories/mfsa2020-49/"
        }
      ],
      "sourceIdentifier": "security@mozilla.org",
      "vulnStatus": "Modified",
      "weaknesses": [
        {
          "description": [
            {
              "lang": "en",
              "value": "CWE-416"
            }
          ],
          "source": "nvd@nist.gov",
          "type": "Primary"
        }
      ]
    },
    "nvd": {
      "cve": {
        "configurations": [
          {
            "nodes": [
              {
                "cpeMatch": [
                  {
                    "criteria": "cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "7F743C78-6F4E-4BD7-A878-B887A2C42BDC",
                    "versionEndExcluding": "82.0.3",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:a:mozilla:firefox_esr:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "08D6779A-1193-446D-AE3E-D859D539A170",
                    "versionEndExcluding": "78.4.1",
                    "vulnerable": true
                  },
                  {
                    "criteria": "cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*",
                    "matchCriteriaId": "635C87C4-E16B-4320-A339-45C8E1DF0401",
                    "versionEndExcluding": "78.4.2",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In certain circumstances, the MCallGetProperty opcode can be emitted with unmet assumptions resulting in an exploitable use-after-free condition. This vulnerability affects Firefox \u003c 82.0.3, Firefox ESR \u003c 78.4.1, and Thunderbird \u003c 78.4.2."
          },
          {
            "lang": "es",
            "value": "En determinadas circunstancias, el opcode MCallGetProperty puede ser emitido con suposiciones no cumplidas, resultando en una condici\u00f3n de uso de la memoria previamente liberada explotable. Esta vulnerabilidad afecta a Firefox versiones anteriores a 82.0.3, Firefox ESR versiones anteriores a 78.4.1, y Thunderbird versiones anteriores a 78.4.2"
          }
        ],
        "id": "CVE-2020-26950",
        "lastModified": "2024-11-21T05:20:33.823",
        "metrics": {
          "cvssMetricV2": [
            {
              "acInsufInfo": false,
              "baseSeverity": "HIGH",
              "cvssData": {
                "accessComplexity": "MEDIUM",
                "accessVector": "NETWORK",
                "authentication": "NONE",
                "availabilityImpact": "COMPLETE",
                "baseScore": 9.3,
                "confidentialityImpact": "COMPLETE",
                "integrityImpact": "COMPLETE",
                "vectorString": "AV:N/AC:M/Au:N/C:C/I:C/A:C",
                "version": "2.0"
              },
              "exploitabilityScore": 8.6,
              "impactScore": 10.0,
              "obtainAllPrivilege": false,
              "obtainOtherPrivilege": false,
              "obtainUserPrivilege": false,
              "source": "nvd@nist.gov",
              "type": "Primary",
              "userInteractionRequired": true
            }
          ],
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 8.8,
                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "REQUIRED",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 2.8,
              "impactScore": 5.9,
              "source": "nvd@nist.gov",
              "type": "Primary"
            }
          ]
        },
        "published": "2020-12-09T01:15:12.503",
        "references": [
          {
            "source": "security@mozilla.org",
            "tags": [
              "Exploit",
              "Third Party Advisory",
              "VDB Entry"
            ],
            "url": "http://packetstormsecurity.com/files/166175/Firefox-MCallGetProperty-Write-Side-Effects-Use-After-Free.html"
          },
          {
            "source": "security@mozilla.org",
            "tags": [
              "Exploit",
              "Issue Tracking",
              "Vendor Advisory"
            ],
            "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1675905"
          },
          {
            "source": "security@mozilla.org",
            "tags": [
              "Vendor Advisory"
            ],
            "url": "https://www.mozilla.org/security/advisories/mfsa2020-49/"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Exploit",
              "Third Party Advisory",
              "VDB Entry"
            ],
            "url": "http://packetstormsecurity.com/files/166175/Firefox-MCallGetProperty-Write-Side-Effects-Use-After-Free.html"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Exploit",
              "Issue Tracking",
              "Vendor Advisory"
            ],
            "url": "https://bugzilla.mozilla.org/show_bug.cgi?id=1675905"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Vendor Advisory"
            ],
            "url": "https://www.mozilla.org/security/advisories/mfsa2020-49/"
          }
        ],
        "sourceIdentifier": "security@mozilla.org",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-416"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Critical",
      "current_release_date": "2025-11-21T16:12:35+00:00",
      "cve": "CVE-2020-26950",
      "id": "CVE-2020-26950",
      "initial_release_date": "2020-11-09T00:00:00+00:00",
      "product_status:fixed": "211",
      "product_status:known_affected": "2",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "Mozilla: Write side effects in MCallGetProperty opcode not accounted for",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2020/cve-2020-26950.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-08-31T02:16:18Z",
      "cve": "CVE-2020-26950",
      "id": "CVE-2020-26950",
      "initial_release_date": "2023-02-15T03:53:01Z",
      "product_status:known_affected": "36",
      "product_status:known_not_affected": "24",
      "product_status:recommended": "401",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2020-26950",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2020-26950.json",
      "version": "25"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.


Loading…

Loading…

Loading…

Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.

Loading…

Detection rules are retrieved from Rulezet.

Loading…

Loading…

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.


Loading…