{"id":"CVE-2020-3511","aliases":["EUVD-2020-24782","GHSA-p84p-mg49-xwvx"],"status":"published","title":"Cisco IOS and IOS XE Software ISDN Q.931 Denial of Service Vulnerability","description":"A vulnerability in the ISDN subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient input validation when the ISDN Q.931 messages are processed. An attacker could exploit this vulnerability by sending a malicious ISDN Q.931 message to an affected device. A successful exploit could allow the attacker to cause the process to crash, resulting in a reload of the affected device.","severity":{"version":"3.0","score":7.4,"vector":"CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-09","score":0.00433,"percentile":0.37905,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-20"],"published":"2020-09-24T17:51:39Z","modified":"2026-06-17T03:18:28Z","products":[{"vendor":"cisco","product":"cisco ios"},{"vendor":"cisco","product":"ios_xe"}],"references":[{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxe-isdn-q931-dos-67eUZBTf","tags":["vendor-advisory","x_refsource_CISCO","x_transferred","Vendor Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2020-3511"},{"url":"https://github.com/advisories/GHSA-p84p-mg49-xwvx"}],"sources":{"cve":[{"id":"CVE-2020-3511","title":"Cisco IOS and IOS XE Software ISDN Q.931 Denial of Service Vulnerability","description":"A vulnerability in the ISDN subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient input validation when the ISDN Q.931 messages are processed. An attacker could exploit this vulnerability by sending a malicious ISDN Q.931 message to an affected device. A successful exploit could allow the attacker to cause the process to crash, resulting in a reload of the affected device.","status":"published","published":"2020-09-24T17:51:39.806Z","modified":"2024-11-13T18:00:40.783Z","cvss":[{"version":"3.0","score":7.4,"vector":"CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high","assessor":"cna"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:35:51.563355Z"}],"euvd":[{"id":"EUVD-2020-24782","description":"A vulnerability in the ISDN subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient input validation when the ISDN Q.931 messages are processed. An attacker could exploit this vulnerability by sending a malicious ISDN Q.931 message to an affected device. A successful exploit could allow the attacker to cause the process to crash, resulting in a reload of the affected device.","status":"published","published":"2020-09-24T17:51:39Z","modified":"2024-11-13T18:00:40Z","cvss":[{"version":"3.0","score":7.4,"vector":"CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high"}],"updated_at":"2026-11-03T00:05:01.673157Z"}],"ghsa":[{"id":"GHSA-p84p-mg49-xwvx","title":"A vulnerability in the ISDN subsystem of Cisco IOS Software and Cisco IOS XE Software could allow...","description":"A vulnerability in the ISDN subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient input validation when the ISDN Q.931 messages are processed. An attacker could exploit this vulnerability by sending a malicious ISDN Q.931 message to an affected device. A successful exploit could allow the attacker to cause the process to crash, resulting in a reload of the affected device.","status":"published","published":"2022-05-24T17:29:29Z","modified":"2023-05-31T05:01:05Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:54:37.773458Z"}],"nvd":[{"id":"CVE-2020-3511","description":"A vulnerability in the ISDN subsystem of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, adjacent attacker to cause a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to insufficient input validation when the ISDN Q.931 messages are processed. An attacker could exploit this vulnerability by sending a malicious ISDN Q.931 message to an affected device. A successful exploit could allow the attacker to cause the process to crash, resulting in a reload of the affected device.","status":"published","published":"2020-09-24T18:15:21.23Z","modified":"2026-06-17T03:18:28.423Z","cvss":[{"version":"3.1","score":7.4,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high","assessor":"primary"},{"version":"3.0","score":7.4,"vector":"CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","level":"high","assessor":"secondary"},{"version":"2.0","score":6.1,"vector":"AV:A/AC:L/Au:N/C:N/I:N/A:C","level":"medium","assessor":"primary"}],"cwes":["CWE-20"],"updated_at":"2026-11-02T14:06:17.70091Z"}]}}