{"cve":"CVE-2024-6640","nvd":{"published":"2024-08-12T13:38:39.380","modified":"2026-06-17T08:18:23.953","status":"Deferred","description":"In ICMPv6 Neighbor Discovery (ND), the ID is always 0.  When pf is configured to allow ND and block incoming Echo Requests, a crafted Echo Request packet after a Neighbor Solicitation (NS) can trigger an Echo Reply.  The packet has to come from the same host as the NS and have a zero as identifier to match the state created by the Neighbor Discovery and allow replies to be generated.\n\nICMPv6 packets with identifier value of zero bypass firewall rules written on the assumption that the incoming packets are going to create a state in the state table.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L","score":6.3},"cwes":["CWE-276"],"references":["https://security.freebsd.org/advisories/FreeBSD-SA-24:05.pf.asc","https://security.netapp.com/advisory/ntap-20240816-0008/"],"products":[],"source":"nvd","synced_at":"2026-10-19T21:53:51.317825789+00:00"},"epss":{"cve":"CVE-2024-6640","score":0.00462,"percentile":0.40081,"date":"2026-10-31"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}