{"id":"CVE-2018-0173","kind":"vulnerability","aliases":["CVE-2018-0173"],"related":[],"title":"Cisco IOS and IOS XE Software: Cisco IOS and IOS XE Software Improper Input Validation Vulnerability","description":"A vulnerability in the Cisco IOS Software and Cisco IOS XE Software function that restores encapsulated option 82 information in DHCP Version 4 (DHCPv4) packets could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a Relay Reply denial of service (DoS) condition. The vulnerability exists because the affected software performs incomplete input validation of encapsulated option 82 information that it receives in DHCPOFFER messages from DHCPv4 servers. An attacker could exploit this vulnerability by sending a crafted DHCPv4 packet to an affected device, which the device would then forward to a DHCPv4 server. When the affected software processes the option 82 information that is encapsulated in the response from the server, an error could occur. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Cisco Bug IDs: CSCvg62754.","summary":"Cisco IOS and IOS XE routers and switches mishandle DHCPv4 packets carrying encapsulated option 82 data during restoration. An attacker can crash or reload the device, causing denial of service.","severity":"high","cvss":8.6,"epss":0.07608,"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-relay-option-82","non-cisco-network"],"how_to_check":null,"fix":"Apply the Cisco IOS and IOS XE updates per vendor instructions (CISA KEV required action). Fixed versions: unknown from sources.","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 Cisco IOS and IOS XE updates per vendor instructions (CISA KEV required action). Fixed versions: unknown from sources.","reach":"network","impact":"low","summary":"Cisco IOS and IOS XE routers and switches mishandle DHCPv4 packets carrying encapsulated option 82 data during restoration. An attacker can crash or reload the device, causing denial of service.","category":"infrastructure","who_cares":["cisco","ios","ios-xe","network-gear","dhcp"],"confidence":0.6,"needs_auth":"unknown","worst_case":"Device crashes or reloads, disrupting network traffic until restored","analyst_note":"Find the Cisco advisory for CVE-2018-0173 (cisco-sa DHCP option 82) to get affected and fixed IOS/IOS XE versions and the exact DHCP configuration required for exposure.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["no-dhcp-relay-option-82","non-cisco-network"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000489,"input_tokens":2877,"output_tokens":402,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-0173':19A,22A '-2018':18A,21A '4':92C '82':54B,87C,132C,176C 'affect':104C,123C,157C,171C,201C 'allow':96C,195C 'and':25A 'attack':59B,100C,144C,197C 'bug':211C 'carri':51B 'caus':66B,102C,199C 'cisco':1A,7A,23A,29B,40B,74C,78C,210C 'condit':117C,209C 'could':95C,145C,189C,194C 'craft':152C 'crash':61B 'cscvg62754':213C 'cve':17A,20A 'data':55B 'denial':67B,113C 'devic':65B,105C,158C,161C,202C 'dhcp':30B,90C 'dhcpoffer':138C 'dhcpv4':49B,93C,141C,153C,167C 'dos':116C,208C 'encapsul':52B,85C,130C,180C 'error':188C 'exist':120C 'exploit':31B,146C,193C 'forward':164C 'function':82C 'gear':39B 'id':212C 'improp':13A 'incomplet':126C 'inform':88C,133C,177C 'infrastructur':32B 'input':14A,127C 'io':2A,4A,8A,10A,33B,35B,41B,43B,75C,79C 'ios':24A,26A 'ios-x':34B 'messag':139C 'mishandl':48B 'network':38B 'network-gear':37B 'occur':190C 'option':53B,86C,131C,175C 'packet':50B,94C,154C 'perform':125C 'process':173C 'receiv':136C 'relay':111C 'reload':63B,107C,204C 'remot':99C 'repli':112C 'respons':183C 'restor':57B,84C 'result':108C,205C 'router':45B 'send':150C 'server':142C,168C,186C 'servic':69B,115C 'softwar':6A,12A,76C,81C,124C,172C 'software':28A 'success':192C 'switch':47B 'unauthent':98C 'valid':15A,128C 'version':91C 'vulner':16A,71C,119C,148C 'would':162C 'xe':5A,11A,27A,36B,44B,80C","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-2018-0173","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2018-0173","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":"2026-10-25T10:39:07+00:00","note":null},{"source":"epss","external_id":"CVE-2018-0173","url":"https://api.first.org/data/v1/epss?cve=CVE-2018-0173","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-2018-0173","url":"https://nvd.nist.gov/vuln/detail/CVE-2018-0173","severity":null,"published_at":"2018-03-28T22:29:01+00:00","modified_at":"2026-06-17T01:30:00+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"}