{"id":"CVE-2026-104421","state":"PUBLISHED","title":"Zebra before 6.2.1 Block Download Denial of Service via KnownBlock SentHashes Lockout","description":"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 honest block's header hash, causing Request::KnownBlock to skip the honest block and keep nodes behind the tip.","publishedAt":"2026-10-02T11:38:02.456Z","updatedAt":"2026-10-02T12:28:10.585Z","severity":{"score":6.9,"label":"Medium","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N","source":"VulnCheck"},"assigner":"VulnCheck","products":["ZcashFoundation zebra"],"affected":[{"vendor":"ZcashFoundation","product":"zebra","packageURL":"pkg:cargo/zebrad","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"6.2.1","versionType":"semver"},{"version":"6.2.1","status":"unaffected","versionType":"semver"}]}],"references":["https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-x93j-mj2f-q338","https://www.vulncheck.com/advisories/zebra-before-6.2.1-block-download-denial-of-service-via-knownblock-senthashes-lockout"],"weaknesses":["CWE-459"],"ingestedAt":"2026-10-29T20:10:23.711Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/104xxx/CVE-2026-104421.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-104421","state":"PUBLISHED","datePublished":"2026-10-02T11:38:02.456Z","dateUpdated":"2026-10-02T12:28:10.585Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-10-02T00:46:23.830Z"},"containers":{"cna":{"title":"Zebra before 6.2.1 Block Download Denial of Service via KnownBlock SentHashes Lockout","descriptions":[{"lang":"en","value":"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 honest block's header hash, causing Request::KnownBlock to skip the honest block and keep nodes behind the tip."}],"affected":[{"vendor":"ZcashFoundation","product":"zebra","packageURL":"pkg:cargo/zebrad","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"6.2.1","versionType":"semver"},{"version":"6.2.1","status":"unaffected","versionType":"semver"}]}],"references":[{"url":"https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-x93j-mj2f-q338","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-x93j-mj2f-q338)"},{"url":"https://www.vulncheck.com/advisories/zebra-before-6.2.1-block-download-denial-of-service-via-knownblock-senthashes-lockout","name":"VulnCheck Advisory: Zebra before 6.2.1 Block Download Denial of Service via KnownBlock SentHashes Lockout","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","cvssV4_0":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"LOW","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":6.9,"baseSeverity":"MEDIUM"}},{"format":"CVSS","cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW","baseScore":5.3,"baseSeverity":"MEDIUM"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-459","lang":"en","description":"Incomplete Cleanup","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-10-02T11:38:02.456Z"},"datePublic":"2026-07-22T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:zfnd:zebra:*:*:*:*:*:*:*:*","versionEndExcluding":"6.2.1"}]}]}],"x_generator":{"engine":"vulncheck-endgame"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-02T12:27:43.846358Z","id":"CVE-2026-104421","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-02T12:28:10.585Z"}}]}}}