{"id":"CVE-2026-104421","title":"Zebra before 6.2.1 contains an incomplete cleanup vulnerability that allows unauthenticated peers to block downloading of valid blocks by leaving rejected hashes in SentHashes","summary":"Zebra before 6.2.1 contains an incomplete cleanup vulnerability that allows unauthenticated peers to block downloading of valid blocks by leaving rejected hashes in SentHashes. Attackers can send a contextually invalid block sharing an h…","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","cwe":["CWE-459"],"vendor":"ZcashFoundation","product":"zebra","affected":["zebra < 6.2.1"],"published":"2026-10-02","updated":"2026-10-02","sourceUpdated":"2026-10-02T13:17:42.550","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-104421","references":[{"url":"https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-x93j-mj2f-q338","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/zebra-before-6.2.1-block-download-denial-of-service-via-knownblock-senthashes-lockout","label":"disclosure@vulncheck.com"}],"tags":["nvd","cve.org"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-02T12:27:43.846358Z"},"ingestedAt":"2026-10-02T12:17:44.329Z","slug":"CVE-2026-104421","body":"## Overview\n\nZebra before 6.2.1 contains an incomplete cleanup vulnerability that allows unauthenticated peers to block downloading of valid blocks by leaving rejected hashes in SentHashes. Attackers can send a contextually invalid block sharing an honest block's header hash, causing Request::KnownBlock to skip the honest block and keep nodes behind the tip.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}