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

CVE-2021-34557 (GCVE-0-2021-34557)

Vulnerability from cvelistv5 – Published: 2021-06-10 15:54 – Updated: 2024-08-04 00:12
VLAI
Summary
XScreenSaver 5.45 can be bypassed if the machine has more than ten disconnectable video outputs. A buffer overflow in update_screen_layout() allows an attacker to bypass the standard screen lock authentication mechanism by crashing XScreenSaver. The attacker must physically disconnect many video outputs.
Severity
4.6 (Medium)
CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
  • n/a
Assigner
References
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2024-08-04T00:12:50.416Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "tags": [
              "x_refsource_MISC",
              "x_transferred"
            ],
            "url": "https://github.com/QubesOS/qubes-issues/issues/6595"
          },
          {
            "tags": [
              "x_refsource_MISC",
              "x_transferred"
            ],
            "url": "https://www.openwall.com/lists/oss-security/2021/06/05/1"
          },
          {
            "tags": [
              "x_refsource_MISC",
              "x_transferred"
            ],
            "url": "https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txt"
          },
          {
            "tags": [
              "x_refsource_MISC",
              "x_transferred"
            ],
            "url": "https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch"
          },
          {
            "name": "[oss-security] 20210611 Re: XScreenSaver 5.45: Disconnecting a video output can cause XScreenSaver to crash and unlock",
            "tags": [
              "mailing-list",
              "x_refsource_MLIST",
              "x_transferred"
            ],
            "url": "http://www.openwall.com/lists/oss-security/2021/06/11/1"
          },
          {
            "name": "[oss-security] 20210706 xscreensaver 5.45 crash",
            "tags": [
              "mailing-list",
              "x_refsource_MLIST",
              "x_transferred"
            ],
            "url": "http://www.openwall.com/lists/oss-security/2021/07/06/2"
          },
          {
            "name": "FEDORA-2021-5af4452ffd",
            "tags": [
              "vendor-advisory",
              "x_refsource_FEDORA",
              "x_transferred"
            ],
            "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/"
          }
        ],
        "title": "CVE Program Container"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "n/a",
          "vendor": "n/a",
          "versions": [
            {
              "status": "affected",
              "version": "n/a"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "XScreenSaver 5.45 can be bypassed if the machine has more than ten disconnectable video outputs. A buffer overflow in update_screen_layout() allows an attacker to bypass the standard screen lock authentication mechanism by crashing XScreenSaver. The attacker must physically disconnect many video outputs."
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "description": "n/a",
              "lang": "en",
              "type": "text"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2021-08-19T02:06:17.000Z",
        "orgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca",
        "shortName": "mitre"
      },
      "references": [
        {
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/QubesOS/qubes-issues/issues/6595"
        },
        {
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://www.openwall.com/lists/oss-security/2021/06/05/1"
        },
        {
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txt"
        },
        {
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch"
        },
        {
          "name": "[oss-security] 20210611 Re: XScreenSaver 5.45: Disconnecting a video output can cause XScreenSaver to crash and unlock",
          "tags": [
            "mailing-list",
            "x_refsource_MLIST"
          ],
          "url": "http://www.openwall.com/lists/oss-security/2021/06/11/1"
        },
        {
          "name": "[oss-security] 20210706 xscreensaver 5.45 crash",
          "tags": [
            "mailing-list",
            "x_refsource_MLIST"
          ],
          "url": "http://www.openwall.com/lists/oss-security/2021/07/06/2"
        },
        {
          "name": "FEDORA-2021-5af4452ffd",
          "tags": [
            "vendor-advisory",
            "x_refsource_FEDORA"
          ],
          "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/"
        }
      ],
      "x_legacyV4Record": {
        "CVE_data_meta": {
          "ASSIGNER": "cve@mitre.org",
          "ID": "CVE-2021-34557",
          "STATE": "PUBLIC"
        },
        "affects": {
          "vendor": {
            "vendor_data": [
              {
                "product": {
                  "product_data": [
                    {
                      "product_name": "n/a",
                      "version": {
                        "version_data": [
                          {
                            "version_value": "n/a"
                          }
                        ]
                      }
                    }
                  ]
                },
                "vendor_name": "n/a"
              }
            ]
          }
        },
        "data_format": "MITRE",
        "data_type": "CVE",
        "data_version": "4.0",
        "description": {
          "description_data": [
            {
              "lang": "eng",
              "value": "XScreenSaver 5.45 can be bypassed if the machine has more than ten disconnectable video outputs. A buffer overflow in update_screen_layout() allows an attacker to bypass the standard screen lock authentication mechanism by crashing XScreenSaver. The attacker must physically disconnect many video outputs."
            }
          ]
        },
        "problemtype": {
          "problemtype_data": [
            {
              "description": [
                {
                  "lang": "eng",
                  "value": "n/a"
                }
              ]
            }
          ]
        },
        "references": {
          "reference_data": [
            {
              "name": "https://github.com/QubesOS/qubes-issues/issues/6595",
              "refsource": "MISC",
              "url": "https://github.com/QubesOS/qubes-issues/issues/6595"
            },
            {
              "name": "https://www.openwall.com/lists/oss-security/2021/06/05/1",
              "refsource": "MISC",
              "url": "https://www.openwall.com/lists/oss-security/2021/06/05/1"
            },
            {
              "name": "https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txt",
              "refsource": "MISC",
              "url": "https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txt"
            },
            {
              "name": "https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch",
              "refsource": "MISC",
              "url": "https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch"
            },
            {
              "name": "[oss-security] 20210611 Re: XScreenSaver 5.45: Disconnecting a video output can cause XScreenSaver to crash and unlock",
              "refsource": "MLIST",
              "url": "http://www.openwall.com/lists/oss-security/2021/06/11/1"
            },
            {
              "name": "[oss-security] 20210706 xscreensaver 5.45 crash",
              "refsource": "MLIST",
              "url": "http://www.openwall.com/lists/oss-security/2021/07/06/2"
            },
            {
              "name": "FEDORA-2021-5af4452ffd",
              "refsource": "FEDORA",
              "url": "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/"
            }
          ]
        }
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "8254265b-2729-46b6-b9e3-3dfca2d5bfca",
    "assignerShortName": "mitre",
    "cveId": "CVE-2021-34557",
    "datePublished": "2021-06-10T15:54:35.000Z",
    "dateReserved": "2021-06-10T00:00:00.000Z",
    "dateUpdated": "2024-08-04T00:12:50.416Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2021-34557",
      "date": "2026-09-18",
      "epss": "0.0048",
      "percentile": "0.40496"
    },
    "nvd": {
      "cve": {
        "configurations": [
          {
            "nodes": [
              {
                "cpeMatch": [
                  {
                    "criteria": "cpe:2.3:a:xscreensaver_project:xscreensaver:5.45:*:*:*:*:*:*:*",
                    "matchCriteriaId": "849AE900-753F-4BF8-9F31-C2EC13605D23",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          },
          {
            "nodes": [
              {
                "cpeMatch": [
                  {
                    "criteria": "cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*",
                    "matchCriteriaId": "E460AA51-FCDA-46B9-AE97-E6676AA5E194",
                    "vulnerable": true
                  }
                ],
                "negate": false,
                "operator": "OR"
              }
            ]
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "XScreenSaver 5.45 can be bypassed if the machine has more than ten disconnectable video outputs. A buffer overflow in update_screen_layout() allows an attacker to bypass the standard screen lock authentication mechanism by crashing XScreenSaver. The attacker must physically disconnect many video outputs."
          },
          {
            "lang": "es",
            "value": "XScreenSaver versi\u00f3n 5.45 puede ser omitido si la m\u00e1quina tiene m\u00e1s de diez salidas de v\u00eddeo desconectables. Un desbordamiento de b\u00fafer en la funci\u00f3n update_screen_layout() permite a un atacante omitir el mecanismo de autenticaci\u00f3n de bloqueo de pantalla est\u00e1ndar, al bloquear a XScreenSaver. El atacante debe desconectar f\u00edsicamente muchas salidas de v\u00eddeo"
          }
        ],
        "id": "CVE-2021-34557",
        "lastModified": "2024-11-21T06:10:40.827",
        "metrics": {
          "cvssMetricV2": [
            {
              "acInsufInfo": false,
              "baseSeverity": "LOW",
              "cvssData": {
                "accessComplexity": "LOW",
                "accessVector": "LOCAL",
                "authentication": "NONE",
                "availabilityImpact": "PARTIAL",
                "baseScore": 2.1,
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "vectorString": "AV:L/AC:L/Au:N/C:N/I:N/A:P",
                "version": "2.0"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 2.9,
              "obtainAllPrivilege": false,
              "obtainOtherPrivilege": false,
              "obtainUserPrivilege": false,
              "source": "nvd@nist.gov",
              "type": "Primary",
              "userInteractionRequired": false
            }
          ],
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "PHYSICAL",
                "availabilityImpact": "HIGH",
                "baseScore": 4.6,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 0.9,
              "impactScore": 3.6,
              "source": "nvd@nist.gov",
              "type": "Primary"
            }
          ]
        },
        "published": "2021-06-10T16:15:08.227",
        "references": [
          {
            "source": "cve@mitre.org",
            "tags": [
              "Mailing List",
              "Third Party Advisory"
            ],
            "url": "http://www.openwall.com/lists/oss-security/2021/06/11/1"
          },
          {
            "source": "cve@mitre.org",
            "tags": [
              "Exploit",
              "Mailing List",
              "Third Party Advisory"
            ],
            "url": "http://www.openwall.com/lists/oss-security/2021/07/06/2"
          },
          {
            "source": "cve@mitre.org",
            "tags": [
              "Issue Tracking",
              "Third Party Advisory"
            ],
            "url": "https://github.com/QubesOS/qubes-issues/issues/6595"
          },
          {
            "source": "cve@mitre.org",
            "tags": [
              "Exploit",
              "Third Party Advisory"
            ],
            "url": "https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txt"
          },
          {
            "source": "cve@mitre.org",
            "tags": [
              "Patch",
              "Third Party Advisory"
            ],
            "url": "https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch"
          },
          {
            "source": "cve@mitre.org",
            "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/"
          },
          {
            "source": "cve@mitre.org",
            "tags": [
              "Exploit",
              "Mailing List",
              "Third Party Advisory"
            ],
            "url": "https://www.openwall.com/lists/oss-security/2021/06/05/1"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Mailing List",
              "Third Party Advisory"
            ],
            "url": "http://www.openwall.com/lists/oss-security/2021/06/11/1"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Exploit",
              "Mailing List",
              "Third Party Advisory"
            ],
            "url": "http://www.openwall.com/lists/oss-security/2021/07/06/2"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Issue Tracking",
              "Third Party Advisory"
            ],
            "url": "https://github.com/QubesOS/qubes-issues/issues/6595"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Exploit",
              "Third Party Advisory"
            ],
            "url": "https://github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-068-2021.txt"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Patch",
              "Third Party Advisory"
            ],
            "url": "https://github.com/QubesOS/qubes-xscreensaver/blob/master/0001-Fix-updating-outputs-info.patch"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "url": "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TC4QB7TRS4GS7LDXQQ4PC6J3LVFJYISV/"
          },
          {
            "source": "af854a3a-2127-422b-91ae-364da2661108",
            "tags": [
              "Exploit",
              "Mailing List",
              "Third Party Advisory"
            ],
            "url": "https://www.openwall.com/lists/oss-security/2021/06/05/1"
          }
        ],
        "sourceIdentifier": "cve@mitre.org",
        "vulnStatus": "Modified",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-120"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
          }
        ]
      }
    },
    "redhat_vex": {
      "current_release_date": "2025-11-21T16:07:14+00:00",
      "cve": "CVE-2021-34557",
      "id": "CVE-2021-34557",
      "initial_release_date": "2021-06-10T00:00:00+00:00",
      "product_status:known_not_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "XScreenSaver: buffer overflow in update_screen_layout() allows an attacker to bypass the standard screen lock authentication",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-34557.json",
      "version": "3"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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.


Detection rules are retrieved from Rulezet.


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.