{"id":"CVE-2026-124740","kind":"vulnerability","aliases":["CVE-2026-124740"],"related":[],"title":"BusyBox udhcpc6: crafted DHCPv6 reply crashes client or leaks memory","description":"A flaw was found in BusyBox's udhcpc6 DHCPv6 client. A malicious server on the local network can trigger a use-after-free condition by responding with a crafted Dynamic Host Configuration Protocol for IPv6 (DHCPv6) reply packet lacking usable address options. This issue causes the client to read stale heap memory, which can result in a Denial of Service (DoS) due to an application crash or disclose previously assigned network address data in subsequent discovery requests.","summary":"BusyBox's udhcpc6 DHCPv6 client can read freed heap memory when a DHCPv6 reply lacks usable address options. A malicious DHCPv6 server on the local network can crash the client or get previously assigned IPv6 address data disclosed in later requests.","severity":"medium","cvss":4.3,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["busybox","dhcpv6","embedded-linux","infrastructure","ipv6"],"not_affected_if":["no-dhcpv6","no-udhcpc6","static-ipv6"],"how_to_check":"- Check the BusyBox version with `busybox --help` or `busybox | head -1`\n- Look for `udhcpc6` on the system, for example with `which udhcpc6` or `ls /sbin/udhcpc6`\n- Confirm whether it is used to get IPv6 addresses on a network interface","fix":null,"status":"open","published_at":"2026-11-11T12:19:47+00:00","first_seen_at":"2026-11-11T12:27:11+00:00","triaged_at":"2026-11-11T12:29:03+00:00","updated_at":"2026-11-11T12:29:03+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-11-11T12:29:03Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"BusyBox udhcpc6: crafted DHCPv6 reply crashes client or leaks memory","impact":"low","summary":"BusyBox's udhcpc6 DHCPv6 client can read freed heap memory when a DHCPv6 reply lacks usable address options. A malicious DHCPv6 server on the local network can crash the client or get previously assigned IPv6 address data disclosed in later requests.","audience":"businesses","category":"infrastructure","nicknames":[],"who_cares":["busybox","embedded-linux","dhcpv6","ipv6"],"confidence":0.6,"fix_status":"unknown","needs_auth":"no","worst_case":"Client crashes or leaks previously assigned IPv6 address data","analyst_note":"Confirm affected and fixed BusyBox versions from the NVD entry or the BusyBox project before writing a fix.","how_to_check":"- Check the BusyBox version with `busybox --help` or `busybox | head -1`\n- Look for `udhcpc6` on the system, for example with `which udhcpc6` or `ls /sbin/udhcpc6`\n- Confirm whether it is used to get IPv6 addresses on a network interface","plain_action":"","product_name":"","needs_analyst":true,"not_affected_if":["no-udhcpc6","static-ipv6","no-dhcpv6"],"who_is_affected":"Systems running BusyBox's udhcpc6 DHCPv6 client to configure IPv6 addresses on a network interface are exposed. The attacker must be a malicious DHCPv6 server on the same local network segment. Systems that do not use udhcpc6 for DHCPv6 can skip it.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"yes","severity_if_unknown":"unknown"},"cost_usd":0.000771,"input_tokens":4604,"output_tokens":622,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-124740':13A,16A '-2026':12A,15A 'address':40B,59B,106C,137C 'applic':130C 'assign':57B,135C 'busybox':1A,17B,24B,70C 'caus':110C 'client':7A,28B,53B,74C,112C 'condit':89C 'configur':97C 'craft':3A,94C 'crash':6A,51B,131C 'cve':11A,14A 'data':60B,138C 'denial':123C 'dhcpv6':4A,18B,27B,36B,44B,73C,101C 'disclos':61B,133C 'discoveri':141C 'dos':126C 'due':127C 'dynam':95C 'embed':20B 'embedded-linux':19B 'flaw':66C 'found':68C 'free':88C 'freed':31B 'get':55B 'heap':32B,116C 'host':96C 'infrastructur':22B 'ipv6':23B,58B,100C 'issu':109C 'lack':38B,104C 'later':63B 'leak':9A 'linux':21B 'local':48B,80C 'malici':43B,76C 'memori':10A,33B,117C 'network':49B,81C,136C 'option':41B,107C 'packet':103C 'previous':56B,134C 'protocol':98C 'read':30B,114C 'repli':5A,37B,102C 'request':64B,142C 'respond':91C 'result':120C 'server':45B,77C 'servic':125C 'stale':115C 'subsequ':140C 'trigger':83C 'udhcpc6':2A,26B,72C 'usabl':39B,105C 'use':86C 'use-after-fre':85C","nicknames":[],"mitigations":[],"who_affected":"Systems running BusyBox's udhcpc6 DHCPv6 client to configure IPv6 addresses on a network interface are exposed. The attacker must be a malicious DHCPv6 server on the same local network segment. Systems that do not use udhcpc6 for DHCPv6 can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"none","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["busybox","dhcpv6","embeddedlinux","infrastructure","ipv6","medium"],"campaign_type":null,"search_a":"'-124740':13A,16A '-2026':12A,15A 'busybox':1A 'client':7A 'craft':3A 'crash':6A 'cve':11A,14A 'dhcpv6':4A 'leak':9A 'memori':10A 'repli':5A 'udhcpc6':2A","search_b":"'address':40B,59B 'assign':57B 'busybox':17B,24B 'client':28B,53B 'crash':51B 'data':60B 'dhcpv6':18B,27B,36B,44B 'disclos':61B 'embed':20B 'embedded-linux':19B 'freed':31B 'get':55B 'heap':32B 'infrastructur':22B 'ipv6':23B,58B 'lack':38B 'later':63B 'linux':21B 'local':48B 'malici':43B 'memori':33B 'network':49B 'option':41B 'previous':56B 'read':30B 'repli':37B 'request':64B 'server':45B 'udhcpc6':26B 'usabl':39B","search_c":"'address':106C,137C 'applic':130C 'assign':135C 'busybox':70C 'caus':110C 'client':74C,112C 'condit':89C 'configur':97C 'craft':94C 'crash':131C 'data':138C 'denial':123C 'dhcpv6':73C,101C 'disclos':133C 'discoveri':141C 'dos':126C 'due':127C 'dynam':95C 'flaw':66C 'found':68C 'free':88C 'heap':116C 'host':96C 'ipv6':100C 'issu':109C 'lack':104C 'local':80C 'malici':76C 'memori':117C 'network':81C,136C 'option':107C 'packet':103C 'previous':134C 'protocol':98C 'read':114C 'repli':102C 'request':142C 'respond':91C 'result':120C 'server':77C 'servic':125C 'stale':115C 'subsequ':140C 'trigger':83C 'udhcpc6':72C 'usabl':105C 'use':86C 'use-after-fre':85C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-11T12:19:47+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","cvss_by":"secalert@redhat.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-124740","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-124740","severity":null,"published_at":"2026-11-11T12:19:47+00:00","modified_at":"2026-11-11T12:19:47+00:00","first_seen_at":"2026-11-11T12:27:11+00:00","fetched_at":"2026-11-11T12:27:11+00:00","note":null}],"documents":[],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}