{"id":"CVE-2021-34767","aliases":["EUVD-2021-21417","GHSA-xwvm-8x4q-gmr9"],"status":"published","title":"Cisco IOS XE Software for Catalyst 9800 Series Wireless Controllers IPv6 Denial of Service Vulnerability","description":"A vulnerability in IPv6 traffic processing of Cisco IOS XE Wireless Controller Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, adjacent attacker to cause a Layer 2 (L2) loop in a configured VLAN, resulting in a denial of service (DoS) condition for that VLAN. The vulnerability is due to a logic error when processing specific link-local IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet that would flow inbound through the wired interface of an affected device. A successful exploit could allow the attacker to cause traffic drops in the affected VLAN, thus triggering the DoS condition.","severity":{"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":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00783,"percentile":0.56492,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":true,"fix_available":false},"cwes":["CWE-670"],"published":"2021-09-23T02:26:47Z","modified":"2026-06-17T03:56:31Z","exploits":[{"source":"pocgithub","id":"lukejenkins/CVE-2021-34767","title":"lukejenkins/CVE-2021-34767","date":"2022-12-20","url":"https://github.com/lukejenkins/CVE-2021-34767"}],"products":[{"vendor":"cisco","product":"cisco ios xe software"},{"vendor":"cisco","product":"ios_xe"}],"references":[{"url":"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ewlc-ipv6-dos-NMYeCnZv","tags":["vendor-advisory","x_refsource_CISCO","x_transferred","Vendor Advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-34767"},{"url":"https://github.com/advisories/GHSA-xwvm-8x4q-gmr9"}],"sources":{"cve":[{"id":"CVE-2021-34767","title":"Cisco IOS XE Software for Catalyst 9800 Series Wireless Controllers IPv6 Denial of Service Vulnerability","description":"A vulnerability in IPv6 traffic processing of Cisco IOS XE Wireless Controller Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, adjacent attacker to cause a Layer 2 (L2) loop in a configured VLAN, resulting in a denial of service (DoS) condition for that VLAN. The vulnerability is due to a logic error when processing specific link-local IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet that would flow inbound through the wired interface of an affected device. A successful exploit could allow the attacker to cause traffic drops in the affected VLAN, thus triggering the DoS condition.","status":"published","published":"2021-09-23T02:26:47.045Z","modified":"2024-11-07T21:58:13.034Z","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":"cna"}],"cwes":["CWE-670"],"updated_at":"2026-11-02T14:33:11.244759Z"}],"euvd":[{"id":"EUVD-2021-21417","description":"A vulnerability in IPv6 traffic processing of Cisco IOS XE Wireless Controller Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, adjacent attacker to cause a Layer 2 (L2) loop in a configured VLAN, resulting in a denial of service (DoS) condition for that VLAN. The vulnerability is due to a logic error when processing specific link-local IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet that would flow inbound through the wired interface of an affected device. A successful exploit could allow the attacker to cause traffic drops in the affected VLAN, thus triggering the DoS condition.","status":"published","published":"2021-09-23T02:26:47Z","modified":"2024-11-07T21:58:13Z","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"}],"updated_at":"2026-11-03T00:05:07.279991Z"}],"ghsa":[{"id":"GHSA-xwvm-8x4q-gmr9","title":"A vulnerability in IPv6 traffic processing of Cisco IOS XE Wireless Controller Software for Cisco...","description":"A vulnerability in IPv6 traffic processing of Cisco IOS XE Wireless Controller Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, adjacent attacker to cause a Layer 2 (L2) loop in a configured VLAN, resulting in a denial of service (DoS) condition for that VLAN. The vulnerability is due to a logic error when processing specific link-local IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet that would flow inbound through the wired interface of an affected device. A successful exploit could allow the attacker to cause traffic drops in the affected VLAN, thus triggering the DoS condition.","status":"published","published":"2022-05-24T19:15:37Z","modified":"2025-10-30T21:30:34Z","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-670"],"updated_at":"2026-11-02T15:04:15.956958Z"}],"nvd":[{"id":"CVE-2021-34767","description":"A vulnerability in IPv6 traffic processing of Cisco IOS XE Wireless Controller Software for Cisco Catalyst 9000 Family Wireless Controllers could allow an unauthenticated, adjacent attacker to cause a Layer 2 (L2) loop in a configured VLAN, resulting in a denial of service (DoS) condition for that VLAN. The vulnerability is due to a logic error when processing specific link-local IPv6 traffic. An attacker could exploit this vulnerability by sending a crafted IPv6 packet that would flow inbound through the wired interface of an affected device. A successful exploit could allow the attacker to cause traffic drops in the affected VLAN, thus triggering the DoS condition.","status":"published","published":"2021-09-23T03:15:20.18Z","modified":"2026-06-17T03:56:31.547Z","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":"secondary"},{"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":"2.0","score":3.3,"vector":"AV:A/AC:L/Au:N/C:N/I:N/A:P","level":"low","assessor":"primary"}],"cwes":["CWE-670"],"updated_at":"2026-11-02T14:06:58.933037Z"}]}}