{"id":"CVE-2026-123559","kind":"vulnerability","aliases":["CVE-2026-123559"],"related":[],"title":"Zebra: crafted transactions stall block verification for minutes, DoS","description":"Zebra before 7.0.0 contains an inefficient algorithmic complexity vulnerability that allows unauthenticated peers to exhaust verification threads by submitting transactions with many transparent inputs. Attackers can relay invalid transactions with tens of thousands of inputs, forcing quadratic ZIP-244 or ZIP-243 digest recomputation that stalls Rayon-backed block verification for minutes.","summary":"Zebra, a Zcash node implementation, does not limit the work needed to verify transactions with many transparent inputs. An unauthenticated peer can relay invalid transactions that force quadratic digest recomputation and stall block verification for minutes.","severity":"high","cvss":8.7,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["runtime","self-hosted","zcash","zebra"],"not_affected_if":["no-public-peer-access","zebra-7.0.0-or-later"],"how_to_check":"- Check the Zebra version in use; affected versions are those before `7.0.0`.\n- Confirm the node accepts peer connections from the public internet.","fix":"- Zebra: move to `7.0.0` or later.","status":"open","published_at":"2026-11-08T02:16:48+00:00","first_seen_at":"2026-11-08T02:21:11+00:00","triaged_at":"2026-11-08T02:23:07+00:00","updated_at":"2026-11-08T02:23:07+00:00","category":"runtime","confidence":0.7,"triage":{"at":"2026-11-08T02:23:07Z","model":"claude-haiku-5-5","output":{"fix":"- Zebra: move to `7.0.0` or later.","reach":"network","title":"Zebra: crafted transactions stall block verification for minutes, DoS","impact":"low","summary":"Zebra, a Zcash node implementation, does not limit the work needed to verify transactions with many transparent inputs. An unauthenticated peer can relay invalid transactions that force quadratic digest recomputation and stall block verification for minutes.","audience":"businesses","category":"runtime","nicknames":[],"who_cares":["zebra","zcash","self-hosted"],"confidence":0.7,"fix_status":"available","needs_auth":"no","worst_case":"Block verification stalls for minutes, degrading node availability","analyst_note":"","how_to_check":"- Check the Zebra version in use; affected versions are those before `7.0.0`.\n- Confirm the node accepts peer connections from the public internet.","plain_action":"","needs_analyst":false,"not_affected_if":["zebra-7.0.0-or-later","no-public-peer-access"],"who_is_affected":"Zebra nodes before `7.0.0` that accept peer connections from the network are exposed, since any unauthenticated peer can trigger the slowdown by relaying crafted transactions. Nodes that only sync from trusted peers behind a firewall are less exposed. Operators running other Zcash implementations are not affected by this entry.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000687,"input_tokens":4311,"output_tokens":512,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-123559':12A,15A '-2026':11A,14A '-243':99C '-244':96C '7.0.0':60C 'algorithm':64C 'allow':68C 'attack':82C 'back':106C 'block':5A,54B,107C 'complex':65C 'contain':61C 'craft':2A 'cve':10A,13A 'digest':50B,100C 'dos':9A 'exhaust':72C 'forc':48B,93C 'host':19B 'implement':26B 'ineffici':63C 'input':39B,81C,92C 'invalid':45B,85C 'limit':29B 'mani':37B,79C 'minut':8A,57B,110C 'need':32B 'node':25B 'peer':42B,70C 'quadrat':49B,94C 'rayon':105C 'rayon-back':104C 'recomput':51B,101C 'relay':44B,84C 'runtim':16B 'self':18B 'self-host':17B 'stall':4A,53B,103C 'submit':76C 'ten':88C 'thousand':90C 'thread':74C 'transact':3A,35B,46B,77C,86C 'transpar':38B,80C 'unauthent':41B,69C 'verif':6A,55B,73C,108C 'verifi':34B 'vulner':66C 'work':31B 'zcash':20B,24B 'zebra':1A,21B,22B,58C 'zip':95C,98C","nicknames":[],"mitigations":[],"who_affected":"Zebra nodes before `7.0.0` that accept peer connections from the network are exposed, since any unauthenticated peer can trigger the slowdown by relaying crafted transactions. Nodes that only sync from trusted peers behind a firewall are less exposed. Operators running other Zcash implementations are not affected by this entry.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["high","runtime","selfhosted","zcash","zebra"],"campaign_type":null,"search_a":"'-123559':12A,15A '-2026':11A,14A 'block':5A 'craft':2A 'cve':10A,13A 'dos':9A 'minut':8A 'stall':4A 'transact':3A 'verif':6A 'zebra':1A","search_b":"'block':54B 'digest':50B 'forc':48B 'host':19B 'implement':26B 'input':39B 'invalid':45B 'limit':29B 'mani':37B 'minut':57B 'need':32B 'node':25B 'peer':42B 'quadrat':49B 'recomput':51B 'relay':44B 'runtim':16B 'self':18B 'self-host':17B 'stall':53B 'transact':35B,46B 'transpar':38B 'unauthent':41B 'verif':55B 'verifi':34B 'work':31B 'zcash':20B,24B 'zebra':21B,22B","search_c":"'-243':99C '-244':96C '7.0.0':60C 'algorithm':64C 'allow':68C 'attack':82C 'back':106C 'block':107C 'complex':65C 'contain':61C 'digest':100C 'exhaust':72C 'forc':93C 'ineffici':63C 'input':81C,92C 'invalid':85C 'mani':79C 'minut':110C 'peer':70C 'quadrat':94C 'rayon':105C 'rayon-back':104C 'recomput':101C 'relay':84C 'stall':103C 'submit':76C 'ten':88C 'thousand':90C 'thread':74C 'transact':77C,86C 'transpar':80C 'unauthent':69C 'verif':73C,108C 'vulner':66C 'zebra':58C 'zip':95C,98C","first_public_at":"2026-10-22T13:38:43+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-123559","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123559","severity":null,"published_at":"2026-11-08T02:16:48+00:00","modified_at":"2026-11-08T02:16:48+00:00","first_seen_at":"2026-11-08T02:21:11+00:00","fetched_at":"2026-11-08T02:21:11+00:00","note":null}],"documents":[{"id":99269,"url":"https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-j4cw-58mj-7w6v","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-10-22T13:38:43+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"},{"id":99270,"url":"https://www.vulncheck.com/advisories/zebra-before-7.0.0-denial-of-service-via-quadratic-sighash-computation","title":"Third-party advisory: www.vulncheck.com","kind":"advisory","source":"nvd","publisher":"research","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Third-party advisory: www.vulncheck.com"}],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}