{"id":"CVE-2026-76505","kind":"vulnerability","aliases":["CVE-2026-76505"],"related":[],"title":"Cisco IOS XR: crafted IPv4 packets can crash ASR 9000 line cards","description":"A vulnerability in the IPv4 packet processing functionality of Cisco IOS XR Software that affects Cisco ASR 9000 and 9900 Series Aggregation Services Routers as well as Cisco ASR 9902 and 9903 Compact High-Performance Routers could allow an unauthenticated, remote attacker to cause network processor (NP) errors, resulting in a line card reset or shutdown and a denial of service (DoS) condition. \r\n\r\nThis vulnerability is due to the incorrect handling of crafted IPv4 packets that are received on an affected line card interface and processed as for-us traffic. The issue can result in an NP reset, causing traffic loss on the affected line card while it recovers. Under repeated reset conditions, the network processor may enter a persistent shutdown state, in which case an explicit line card reload may be required to restore traffic.\r\nThe vulnerability is within the IPv4 packet-processing path. Transit IPv4 traffic does not trigger this issue and IPv6 traffic cannot trigger it.","summary":"Crafted IPv4 packets sent to an affected line card interface and processed as for-us traffic can make the network processor error, reset, or shut down. An unauthenticated remote attacker can cause a line card reset or persistent shutdown, causing denial of service and traffic loss.","severity":"high","cvss":7.5,"epss":0.00342,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["asr-9000","cisco","infrastructure","ios-xr","network-routers"],"not_affected_if":["ipv6-only-traffic","transit-only-traffic"],"how_to_check":"- Check the running IOS XR release with `show version` on ASR 9000, 9900, 9902 and 9903 routers and compare it with the fixed releases in the Cisco advisory\n- unknown for other checks, the sources do not say","fix":"- Move ASR 9000, 9900, 9902 and 9903 routers to a fixed IOS XR release named in the Cisco advisory\n- unknown for the exact fixed version, the sources do not say","status":"open","published_at":"2026-10-21T17:19:09+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","triaged_at":"2026-10-25T03:16:29+00:00","updated_at":"2026-10-25T03:16:29+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-25T03:16:29Z","model":"claude-haiku-5-5","output":{"fix":"- Move ASR 9000, 9900, 9902 and 9903 routers to a fixed IOS XR release named in the Cisco advisory\n- unknown for the exact fixed version, the sources do not say","reach":"network","title":"Cisco IOS XR: crafted IPv4 packets can crash ASR 9000 line cards","impact":"medium","summary":"Crafted IPv4 packets sent to an affected line card interface and processed as for-us traffic can make the network processor error, reset, or shut down. An unauthenticated remote attacker can cause a line card reset or persistent shutdown, causing denial of service and traffic loss.","category":"infrastructure","nicknames":[],"who_cares":["cisco","ios-xr","asr-9000","network-routers"],"confidence":0.6,"needs_auth":"no","worst_case":"Line card resets and may stay shut down until manually reloaded","analyst_note":"Check Cisco's advisory for affected and fixed IOS XR releases and any workaround, since the sources here give none.","how_to_check":"- Check the running IOS XR release with `show version` on ASR 9000, 9900, 9902 and 9903 routers and compare it with the fixed releases in the Cisco advisory\n- unknown for other checks, the sources do not say","needs_analyst":true,"not_affected_if":["ipv6-only-traffic","transit-only-traffic"],"who_is_affected":"Operators of Cisco ASR 9000 and 9900 Series Aggregation Services Routers and ASR 9902 and 9903 Compact routers running affected IOS XR software. The flaw is reached by IPv4 packets addressed to the router's line card interfaces, so exposure depends on whether those interfaces accept traffic from untrusted networks. Transit IPv4 traffic does not trigger it and IPv6 traffic cannot trigger it.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"high"},"cost_usd":0.000698,"input_tokens":3611,"output_tokens":673,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-2026':14A,17A '-76505':15A,18A '-9000':20B '9000':10A,93C '9900':95C '9902':105C '9903':107C 'affect':35B,90C,157C,181C 'aggreg':97C 'allow':114C 'asr':9A,19B,92C,104C 'attack':59B,118C 'cannot':235C 'card':12A,37B,64B,129C,159C,183C,206C 'case':202C 'caus':61B,69B,120C,176C 'cisco':1A,21B,85C,91C,103C 'compact':108C 'condit':139C,190C 'could':113C 'craft':4A,29B,149C 'crash':8A 'cve':13A,16A 'denial':70B,135C 'dos':138C 'due':143C 'enter':195C 'error':51B,124C 'explicit':204C 'for-us':42B,164C 'function':83C 'handl':147C 'high':110C 'high-perform':109C 'incorrect':146C 'infrastructur':22B 'interfac':38B,160C 'io':2A,24B,86C 'ios-xr':23B 'ipv4':5A,30B,80C,150C,219C,225C 'ipv6':233C 'issu':169C,231C 'line':11A,36B,63B,128C,158C,182C,205C 'loss':75B,178C 'make':47B 'may':194C,208C 'network':27B,49B,121C,192C 'network-rout':26B 'np':123C,174C 'packet':6A,31B,81C,151C,221C 'packet-process':220C 'path':223C 'perform':111C 'persist':67B,197C 'process':40B,82C,162C,222C 'processor':50B,122C,193C 'receiv':154C 'recov':186C 'reload':207C 'remot':58B,117C 'repeat':188C 'requir':210C 'reset':52B,65B,130C,175C,189C 'restor':212C 'result':125C,171C 'router':28B,99C,112C 'sent':32B 'seri':96C 'servic':72B,98C,137C 'shut':54B 'shutdown':68B,132C,198C 'softwar':88C 'state':199C 'traffic':45B,74B,167C,177C,213C,226C,234C 'transit':224C 'trigger':229C,236C 'unauthent':57B,116C 'us':44B,166C 'vulner':77C,141C,215C 'well':101C 'within':217C 'xr':3A,25B,87C","nicknames":[],"mitigations":[],"who_affected":"Operators of Cisco ASR 9000 and 9900 Series Aggregation Services Routers and ASR 9902 and 9903 Compact routers running affected IOS XR software. The flaw is reached by IPv4 packets addressed to the router's line card interfaces, so exposure depends on whether those interfaces accept traffic from untrusted networks. Transit IPv4 traffic does not trigger it and IPv6 traffic cannot trigger it.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-21T17:19:09+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cvss_by":"psirt@cisco.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-76505","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-76505","severity":null,"published_at":"2026-10-21T17:19:09+00:00","modified_at":"2026-10-22T14:17:49+00:00","first_seen_at":"2026-10-23T21:57:29+00:00","fetched_at":"2026-10-23T22:29:01+00:00","note":null},{"source":"epss","external_id":"CVE-2026-76505","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-76505","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T13:15:54+00:00","fetched_at":"2026-10-24T13:15:54+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"}