{"id":"CVE-2018-0172","kind":"vulnerability","aliases":["CVE-2018-0172"],"related":[],"title":"Cisco IOS and IOS XE Software: Cisco IOS and IOS XE Software Improper Input Validation Vulnerability","description":"A vulnerability in the DHCP option 82 encapsulation functionality of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a denial of service (DoS) condition. The vulnerability exists because the affected software performs incomplete input validation of option 82 information that it receives in DHCP Version 4 (DHCPv4) packets from DHCP relay agents. An attacker could exploit this vulnerability by sending a crafted DHCPv4 packet to an affected device. A successful exploit could allow the attacker to cause a heap overflow condition on the affected device, which will cause the device to reload and result in a DoS condition. Cisco Bug IDs: CSCvg62730.","summary":"A flaw in how Cisco IOS and IOS XE handle DHCP option 82 encapsulation lets a crafted input crash the device, causing denial of service. CISA lists it as exploited in the wild.","severity":"high","cvss":8.6,"epss":0.0782,"exploited":true,"exploited_at":"2022-03-03T00:00:00+00:00","products":[{"name":"Cisco IOS and IOS XE Software","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["cisco","dhcp","exploited","infrastructure","ios","ios-xe","network-gear"],"not_affected_if":["no-dhcp-option-82","non-cisco-hardware"],"how_to_check":"Run 'show version' on each Cisco IOS or IOS XE device and compare against the fixed release in the Cisco advisory; check whether DHCP relay or option 82 handling is configured.","fix":"Apply the update from Cisco's security advisory for the affected IOS or IOS XE train, per CISA's required action.","status":"open","published_at":"2018-03-28T22:29:01+00:00","first_seen_at":"2026-10-23T19:11:52+00:00","triaged_at":"2026-10-23T21:24:18+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:24:18Z","model":"claude-haiku-5-5","output":{"fix":"Apply the update from Cisco's security advisory for the affected IOS or IOS XE train, per CISA's required action.","reach":"network","impact":"medium","summary":"A flaw in how Cisco IOS and IOS XE handle DHCP option 82 encapsulation lets a crafted input crash the device, causing denial of service. CISA lists it as exploited in the wild.","category":"infrastructure","who_cares":["cisco","ios","ios-xe","network-gear","dhcp"],"confidence":0.6,"needs_auth":"unknown","worst_case":"Attacker crashes or reloads the device, disrupting network service.","analyst_note":"Confirm affected and fixed IOS/IOS XE versions and the exact option 82 trigger conditions from the Cisco advisory for CVE-2018-0172.","how_to_check":"Run 'show version' on each Cisco IOS or IOS XE device and compare against the fixed release in the Cisco advisory; check whether DHCP relay or option 82 handling is configured.","needs_analyst":true,"not_affected_if":["no-dhcp-option-82","non-cisco-hardware"],"user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.0005,"input_tokens":2860,"output_tokens":428,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-0172':19A,22A '-2018':18A,21A '4':133C '82':52B,79C,125C 'affect':100C,117C,154C,171C 'agent':139C 'allow':92C,160C 'and':25A 'attack':96C,141C,162C 'bug':187C 'caus':61B,98C,164C,175C 'cisa':65B 'cisco':1A,7A,23A,29B,44B,83C,87C,186C 'condit':111C,168C,185C 'could':91C,142C,159C 'craft':56B,149C 'crash':58B 'cscvg62730':189C 'cve':17A,20A 'denial':62B,107C 'devic':60B,101C,155C,172C,177C 'dhcp':30B,50B,77C,131C,137C 'dhcpv4':134C,150C 'dos':110C,184C 'encapsul':53B,80C 'exist':114C 'exploit':31B,69B,143C,158C 'flaw':41B 'function':81C 'gear':39B 'handl':49B 'heap':166C 'id':188C 'improp':13A 'incomplet':120C 'inform':126C 'infrastructur':32B 'input':14A,57B,121C 'io':2A,4A,8A,10A,33B,35B,45B,47B,84C,88C 'ios':24A,26A 'ios-x':34B 'let':54B 'list':66B 'network':38B 'network-gear':37B 'option':51B,78C,124C 'overflow':167C 'packet':135C,151C 'perform':119C 'receiv':129C 'relay':138C 'reload':103C,179C 'remot':95C 'result':104C,181C 'send':147C 'servic':64B,109C 'softwar':6A,12A,85C,90C,118C 'software':28A 'success':157C 'unauthent':94C 'valid':15A,122C 'version':132C 'vulner':16A,74C,113C,145C 'wild':72B 'xe':5A,11A,27A,36B,48B,89C","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2018-03-28T22:29:01+00:00","kev":{"dateAdded":"2022-03-03","dueDate":"2022-03-17","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H","cvss_by":"nvd@nist.gov","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2018-0172","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2018-0172","severity":null,"published_at":"2022-03-03T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:52+00:00","fetched_at":"2026-10-25T20:35:37+00:00","note":null},{"source":"epss","external_id":"CVE-2018-0172","url":"https://api.first.org/data/v1/epss?cve=CVE-2018-0172","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-23T19:13:44+00:00","fetched_at":"2026-10-23T19:13:44+00:00","note":null},{"source":"nvd","external_id":"CVE-2018-0172","url":"https://nvd.nist.gov/vuln/detail/CVE-2018-0172","severity":null,"published_at":"2018-03-28T22:29:01+00:00","modified_at":"2026-06-17T01:29:59+00:00","first_seen_at":"2026-10-23T21:57:35+00:00","fetched_at":"2026-10-23T21:57:35+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"}