{"id":"CVE-2021-27861","aliases":["EUVD-2021-14599","GHSA-wcc2-hc4j-m2wc"],"status":"published","title":"L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths","description":"Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)","severity":{"version":"3.1","score":4.7,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","level":"medium","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-12","score":0.00663,"percentile":0.52215,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-130","CWE-290"],"published":"2022-09-27T18:40:13Z","modified":"2026-06-17T03:45:32Z","products":[{"vendor":"ieee","product":"802.2"},{"vendor":"ieee","product":"ieee_802.2"},{"vendor":"ietf","product":"draft-ietf-v6ops-ra-guard"},{"vendor":"ietf","product":"p802.1q"}],"references":[{"url":"https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/","tags":["x_transferred","Third Party Advisory"]},{"url":"https://standards.ieee.org/ieee/802.2/1048/","tags":["x_transferred","Third Party Advisory"]},{"url":"https://standards.ieee.org/ieee/802.1Q/10323/","tags":["x_transferred","Third Party Advisory"]},{"url":"https://kb.cert.org/vuls/id/855201","tags":["x_transferred"]},{"url":"https://blog.champtar.fr/VLAN0_LLC_SNAP/","tags":["x_transferred"]},{"url":"https://www.kb.cert.org/vuls/id/855201"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-27861"},{"url":"https://blog.champtar.fr/VLAN0_LLC_SNAP"},{"url":"https://datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08"},{"url":"https://standards.ieee.org/ieee/802.1Q/10323"},{"url":"https://standards.ieee.org/ieee/802.2/1048"},{"url":"https://github.com/advisories/GHSA-wcc2-hc4j-m2wc"}],"sources":{"cve":[{"id":"CVE-2021-27861","title":"L2 network filtering bypass using stacked VLAN0 and LLC/SNAP headers with invalid lengths","description":"Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)","status":"published","published":"2022-09-27T18:40:13.742Z","modified":"2025-11-04T19:12:27.712Z","cvss":[{"version":"3.1","score":4.7,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","level":"medium","assessor":"adp"}],"cwes":["CWE-130","CWE-290"],"updated_at":"2026-11-02T14:33:04.360272Z"}],"euvd":[{"id":"EUVD-2021-14599","description":"Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)","status":"published","published":"2022-09-27T18:40:13Z","modified":"2025-11-04T19:12:27Z","cvss":[{"version":"3.1","score":4.7,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","level":"medium"}],"updated_at":"2026-11-02T19:49:23.324829Z"}],"ghsa":[{"id":"GHSA-wcc2-hc4j-m2wc","title":"Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP...","description":"Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)","status":"published","published":"2022-09-28T00:00:18Z","modified":"2025-11-04T21:31:32Z","cvss":[{"version":"3.1","score":4.7,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","level":"medium"}],"cwes":["CWE-130","CWE-290"],"updated_at":"2026-11-02T15:04:37.024156Z"}],"nvd":[{"id":"CVE-2021-27861","description":"Layer 2 network filtering capabilities such as IPv6 RA guard can be bypassed using LLC/SNAP headers with invalid length (and optionally VLAN0 headers)","status":"published","published":"2022-09-27T19:15:09.33Z","modified":"2026-06-17T03:45:32.467Z","cvss":[{"version":"3.1","score":4.7,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","level":"medium","assessor":"primary"},{"version":"3.1","score":4.7,"vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","level":"medium","assessor":"secondary"}],"cwes":["CWE-130","CWE-290"],"updated_at":"2026-11-02T14:07:06.906968Z"}]}}