{"id":"CVE-2026-112112","kind":"vulnerability","aliases":["CVE-2026-112112"],"related":[],"title":"BIRD routing daemon: IPv6 FlowSpec check lets peers inject out-of-scope rules","description":"An IPv6 FlowSpec validation bypass in the CZ.NIC BIRD Internet Routing Daemon allows an established BGP peer to inject FlowSpec rules matching destinations outside the address space authorized by the unicast-route validation procedure. With validation enabled on the receiving flow6 channel, BIRD fails to reject a destination prefix component with a nonzero offset, contrary to RFC 8956 section 5. It validates a reconstructed prefix with zero-filled skipped bits, although the original FlowSpec component can match a broader set of IPv6 addresses. Given a suitable unicast route from the peer, the rule can pass validation and, where export policy permits, be propagated to downstream peers. Downstream enforcement may cause unauthorized traffic filtering or redirection.","summary":"BIRD, the CZ.NIC BGP routing daemon, fails to reject IPv6 FlowSpec destination prefixes with a nonzero offset when validation is enabled on a flow6 channel. An established BGP peer can get rules matching address space it is not authorized for, which may then propagate to downstream peers and filter or redirect traffic.","severity":"low","cvss":2.3,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["bgp","bird","flowspec","ipv6","network-operators","runtime"],"not_affected_if":["ipv4-only","no-flow6-channel","no-flowspec","validation-disabled"],"how_to_check":"- Run `birdc show protocols all` and check whether any BGP peer has a flow6 channel with FlowSpec import and validation enabled.\n- Check the installed BIRD version with `bird --version` (or `birdc show status`) and compare it against the fixed release named in the NVD record.","fix":"- Upgrade BIRD to the fixed release listed for CVE-2026-112112 (exact version unknown from the sources).\n- Until patched, restrict which peers may send FlowSpec routes and tighten export policy for flow6 channels.","status":"open","published_at":"2026-10-18T23:16:56+00:00","first_seen_at":"2026-10-23T21:57:17+00:00","triaged_at":"2026-10-25T04:49:54+00:00","updated_at":"2026-10-25T04:49:54+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-10-25T04:49:54Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade BIRD to the fixed release listed for CVE-2026-112112 (exact version unknown from the sources).\n- Until patched, restrict which peers may send FlowSpec routes and tighten export policy for flow6 channels.","reach":"network","title":"BIRD routing daemon: IPv6 FlowSpec check lets peers inject out-of-scope rules","impact":"medium","summary":"BIRD, the CZ.NIC BGP routing daemon, fails to reject IPv6 FlowSpec destination prefixes with a nonzero offset when validation is enabled on a flow6 channel. An established BGP peer can get rules matching address space it is not authorized for, which may then propagate to downstream peers and filter or redirect traffic.","category":"runtime","nicknames":[],"who_cares":["bird","bgp","network-operators","ipv6","flowspec"],"confidence":0.6,"needs_auth":"yes","worst_case":"Peer injects FlowSpec rules that filter or redirect downstream traffic","analyst_note":"Find the fixed BIRD version and advisory text from the NVD record (https://nvd.nist.gov/vuln/detail/CVE-2026-112112) and the BIRD project announcements.","how_to_check":"- Run `birdc show protocols all` and check whether any BGP peer has a flow6 channel with FlowSpec import and validation enabled.\n- Check the installed BIRD version with `bird --version` (or `birdc show status`) and compare it against the fixed release named in the NVD record.","needs_analyst":true,"not_affected_if":["no-flowspec","ipv4-only","no-flow6-channel","validation-disabled"],"who_is_affected":"Only networks running BIRD as a BGP speaker that accept IPv6 FlowSpec from peers on a flow6 channel with validation enabled. Exposure depends on a valid unicast route from that peer and on export policy that forwards the rules downstream. Teams using BIRD only for IPv4 unicast, or without flow6 channels, can skip it.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"low"},"cost_usd":0.000719,"input_tokens":3494,"output_tokens":739,"severity_before":"low"},"analyst_status":null,"analyst_note":null,"search":"'-112112':17A,20A '-2026':16A,19A '5':141C '8956':139C 'address':62B,106C,165C 'allow':93C 'although':153C 'author':67B,108C 'bgp':21B,32B,56B,96C 'bird':1A,22B,29B,89C,124C 'bit':152C 'broader':161C 'bypass':85C 'caus':192C 'channel':53B,123C 'check':6A 'compon':131C,157C 'contrari':136C 'cve':15A,18A 'cz.nic':31B,88C 'daemon':3A,34B,92C 'destin':40B,103C,129C 'downstream':74B,187C,189C 'enabl':49B,118C 'enforc':190C 'establish':55B,95C 'export':181C 'fail':35B,125C 'fill':150C 'filter':77B,195C 'flow6':52B,122C 'flowspec':5A,23B,39B,83C,100C,156C 'get':59B 'given':166C 'inject':9A,99C 'internet':90C 'ipv6':4A,24B,38B,82C,164C 'let':7A 'match':61B,102C,159C 'may':70B,191C 'network':26B 'network-oper':25B 'nonzero':44B,134C 'offset':45B,135C 'oper':27B 'origin':155C 'out-of-scop':10A 'outsid':104C 'pass':177C 'peer':8A,57B,75B,97C,173C,188C 'permit':183C 'polici':182C 'prefix':41B,130C,146C 'procedur':115C 'propag':72B,185C 'receiv':121C 'reconstruct':145C 'redirect':79B,197C 'reject':37B,127C 'rfc':138C 'rout':2A,33B,91C,113C,170C 'rule':14A,60B,101C,175C 'runtim':28B 'scope':13A 'section':140C 'set':162C 'skip':151C 'space':63B,107C 'suitabl':168C 'traffic':80B,194C 'unauthor':193C 'unicast':112C,169C 'unicast-rout':111C 'valid':47B,84C,114C,117C,143C,178C 'zero':149C 'zero-fil':148C","nicknames":[],"mitigations":[],"who_affected":"Only networks running BIRD as a BGP speaker that accept IPv6 FlowSpec from peers on a flow6 channel with validation enabled. Exposure depends on a valid unicast route from that peer and on export policy that forwards the rules downstream. Teams using BIRD only for IPv4 unicast, or without flow6 channels, can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-18T23:16:56+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:N/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":"cve@mitre.org","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-112112","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-112112","severity":null,"published_at":"2026-10-18T23:16:56+00:00","modified_at":"2026-10-19T21:14:14+00:00","first_seen_at":"2026-10-23T21:57:17+00:00","fetched_at":"2026-10-23T22:28:56+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}