{"id":"CVE-2026-20221","aliases":["EUVD-2026-107378","GHSA-vm6m-qmxg-cg2c"],"status":"published","title":"Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities","description":"Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine.\r\n\r\nThis vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the  section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required.","severity":{"version":"3.1","score":5.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00577,"percentile":0.48003,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-476"],"published":"2026-10-21T16:12:53Z","modified":"2026-10-22T19:11:26Z","products":[{"vendor":"cisco","product":"cisco cyber vision"},{"vendor":"cisco","product":"cisco open source snort3"},{"vendor":"cisco","product":"cisco secure firewall threat defense (ftd) software"},{"vendor":"cisco","product":"cisco umbrella insights virtual appliance"},{"vendor":"cisco","product":"cisco utd snort ips engine software"}],"references":[{"url":"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-snort3-gre-JNpMHrTv"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-20221"},{"url":"https://github.com/advisories/GHSA-vm6m-qmxg-cg2c"}],"sources":{"cve":[{"id":"CVE-2026-20221","title":"Multiple Cisco Products Snort 3 Generic Routing Encapsulation Denial of Service Vulnerabilities","description":"Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine.\r\n\r\nThis vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the  section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required.","status":"published","published":"2026-10-21T16:12:53.435Z","modified":"2026-10-22T19:11:26.546Z","cvss":[{"version":"3.1","score":5.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L","level":"medium","assessor":"cna"}],"cwes":["CWE-476"],"updated_at":"2026-11-02T13:35:44.571002Z"}],"euvd":[{"id":"EUVD-2026-107378","description":"Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine.\r\n\r\nThis vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the  section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required.","status":"published","published":"2026-10-21T16:12:53Z","modified":"2026-10-22T19:11:26Z","cvss":[{"version":"3.1","score":5.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T16:59:34.021826Z"}],"ghsa":[{"id":"GHSA-vm6m-qmxg-cg2c","title":"Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE...","description":"Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine.\n\nThis vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the  section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required.","status":"published","published":"2026-10-21T18:33:17Z","modified":"2026-10-21T18:33:23Z","cvss":[{"version":"3.1","score":5.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-476"],"updated_at":"2026-11-02T15:14:13.106716Z"}],"nvd":[{"id":"CVE-2026-20221","description":"Multiple Cisco products are affected by a vulnerability in the generic routing encapsulation (GRE) tunnel decapsulation feature of the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause an unexpected restart of the Snort 3 Detection Engine.\r\n\r\nThis vulnerability is due to improper handling of nested GRE traffic. An attacker could exploit this vulnerability by sending a crafted GRE payload through an affected device. A successful exploit could allow the attacker to trigger an unexpected reload of the Snort 3 Detection Engine, resulting in either a bypass or denial of service (DoS) condition, depending on device configuration. For more information, see the  section of this advisory. The Snort 3 Detection Engine will restart automatically. No manual intervention is required.","status":"published","published":"2026-10-21T17:18:27.947Z","modified":"2026-10-22T14:17:40.94Z","cvss":[{"version":"3.1","score":5.8,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L","level":"medium","assessor":"secondary"}],"cwes":["CWE-476"],"updated_at":"2026-11-02T14:13:02.371082Z"}]}}