{"id":"CVE-2026-123557","kind":"vulnerability","aliases":["CVE-2026-123557"],"related":[],"title":"Zebra zebrad: remote peers can crash syncing nodes via race condition","description":"ZcashFoundation Zebra zebrad before 7.0.0 contains a reachable assertion race condition that allows unauthenticated remote peers to abort the node by triggering disconnection during a blocked outbound send. Malicious peers can return empty FindBlocks or FindHeaders replies and stop reading their socket, dropping an unresolved MustUseClientResponseSender and terminating syncing nodes.","summary":"Zebra's zebrad node before 7.0.0 has a reachable assertion race condition. An unauthenticated remote peer can make a syncing node abort by sending empty FindBlocks or FindHeaders replies and stopping reads on its socket.","severity":"high","cvss":8.2,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["package","self-hosted","zcash","zebra","zebrad"],"not_affected_if":["not-syncing","zebrad-7.0.0-or-later"],"how_to_check":"- Check the installed zebrad version (`zebrad --version`) and compare it with the fixed version in the product ranges; versions before `7.0.0` are affected.\n- Confirm whether the node is syncing and reachable from peers on the network.","fix":"- Upgrade zebrad to `7.0.0` or later.","status":"open","published_at":"2026-11-08T02:16:47+00:00","first_seen_at":"2026-11-08T02:21:11+00:00","triaged_at":"2026-11-08T02:23:19+00:00","updated_at":"2026-11-08T02:23:19+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-11-08T02:23:19Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade zebrad to `7.0.0` or later.","reach":"internet","title":"Zebra zebrad: remote peers can crash syncing nodes via race condition","impact":"low","summary":"Zebra's zebrad node before 7.0.0 has a reachable assertion race condition. An unauthenticated remote peer can make a syncing node abort by sending empty FindBlocks or FindHeaders replies and stopping reads on its socket.","audience":"businesses","category":"package","nicknames":[],"who_cares":["zebra","zebrad","zcash","self-hosted"],"confidence":0.7,"fix_status":"available","needs_auth":"no","worst_case":"Remote peer aborts the syncing node, stopping block synchronization","analyst_note":"","how_to_check":"- Check the installed zebrad version (`zebrad --version`) and compare it with the fixed version in the product ranges; versions before `7.0.0` are affected.\n- Confirm whether the node is syncing and reachable from peers on the network.","plain_action":"","needs_analyst":false,"not_affected_if":["zebrad-7.0.0-or-later","not-syncing"],"who_is_affected":"Teams that run a Zebra zebrad node that accepts inbound peer connections while syncing. Any node reachable from untrusted peers can be affected; nodes that only use trusted peers or are not exposed to the network are less at risk. The sources do not describe a configuration that prevents exposure.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000701,"input_tokens":4308,"output_tokens":541,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-123557':14A,17A '-2026':13A,16A '7.0.0':30B,64C 'abort':46B,77C 'allow':72C 'assert':34B,68C 'block':85C 'condit':11A,36B,70C 'contain':65C 'crash':6A 'cve':12A,15A 'disconnect':82C 'drop':102C 'empti':49B,92C 'findblock':50B,93C 'findhead':52B,95C 'host':21B 'make':42B 'malici':88C 'mustuseclientresponsesend':105C 'node':8A,28B,45B,79C,109C 'outbound':86C 'packag':18B 'peer':4A,40B,75C,89C 'race':10A,35B,69C 'reachabl':33B,67C 'read':56B,99C 'remot':3A,39B,74C 'repli':53B,96C 'return':91C 'self':20B 'self-host':19B 'send':48B,87C 'socket':59B,101C 'stop':55B,98C 'sync':7A,44B,108C 'termin':107C 'trigger':81C 'unauthent':38B,73C 'unresolv':104C 'via':9A 'zcash':22B 'zcashfound':60C 'zebra':1A,23B,25B,61C 'zebrad':2A,24B,27B,62C","nicknames":[],"mitigations":[],"who_affected":"Teams that run a Zebra zebrad node that accepts inbound peer connections while syncing. Any node reachable from untrusted peers can be affected; nodes that only use trusted peers or are not exposed to the network are less at risk. The sources do not describe a configuration that prevents exposure.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["high","package","selfhosted","zcash","zebra","zebrad"],"campaign_type":null,"search_a":"'-123557':14A,17A '-2026':13A,16A 'condit':11A 'crash':6A 'cve':12A,15A 'node':8A 'peer':4A 'race':10A 'remot':3A 'sync':7A 'via':9A 'zebra':1A 'zebrad':2A","search_b":"'7.0.0':30B 'abort':46B 'assert':34B 'condit':36B 'empti':49B 'findblock':50B 'findhead':52B 'host':21B 'make':42B 'node':28B,45B 'packag':18B 'peer':40B 'race':35B 'reachabl':33B 'read':56B 'remot':39B 'repli':53B 'self':20B 'self-host':19B 'send':48B 'socket':59B 'stop':55B 'sync':44B 'unauthent':38B 'zcash':22B 'zebra':23B,25B 'zebrad':24B,27B","search_c":"'7.0.0':64C 'abort':77C 'allow':72C 'assert':68C 'block':85C 'condit':70C 'contain':65C 'disconnect':82C 'drop':102C 'empti':92C 'findblock':93C 'findhead':95C 'malici':88C 'mustuseclientresponsesend':105C 'node':79C,109C 'outbound':86C 'peer':75C,89C 'race':69C 'reachabl':67C 'read':99C 'remot':74C 'repli':96C 'return':91C 'send':87C 'socket':101C 'stop':98C 'sync':108C 'termin':107C 'trigger':81C 'unauthent':73C 'unresolv':104C 'zcashfound':60C 'zebra':61C 'zebrad':62C","first_public_at":"2026-10-22T12:27:28+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:H/AT:P/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-2026-123557","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-123557","severity":null,"published_at":"2026-11-08T02:16:47+00:00","modified_at":"2026-11-08T02:16:47+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":99265,"url":"https://github.com/ZcashFoundation/zebra/security/advisories/GHSA-6v36-c42v-v98p","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-10-22T12:27:28+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"},{"id":99266,"url":"https://www.vulncheck.com/advisories/zebra-zebrad-before-7.0.0-reachable-assertion-dos-via-peer-disconnection","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"}