{"id":"CVE-2026-115449","kind":"vulnerability","aliases":["CVE-2026-115449"],"related":[],"title":"libslirp: ICMP echo reply leaks host IP to guest","description":"A flaw was found in libslirp. When handling ICMP echo requests, the reply length is not updated to match the actual data received from the host. Under specific conditions where the normal ICMP socket is unavailable, this length mismatch causes the host's real IP address to be leaked to the guest in the echo reply, breaking the NAT isolation that user-mode networking is expected to provide.","summary":"libslirp, the user-mode networking library used by QEMU and similar tools, mishandles ICMP echo replies when the normal ICMP socket is unavailable. A reply length mismatch leaks the host's real IP address to the guest, breaking NAT isolation.","severity":"low","cvss":3.5,"epss":0.00226,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["infrastructure","libslirp","qemu","self-hosted","virtualization"],"not_affected_if":["bridged-or-tap-networking","no-user-mode-networking"],"how_to_check":"- unknown","fix":"- unknown","status":"open","published_at":"2026-10-22T22:18:06+00:00","first_seen_at":"2026-10-23T21:57:32+00:00","triaged_at":"2026-10-25T04:45:34+00:00","updated_at":"2026-10-25T04:45:34+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-25T04:45:34Z","model":"claude-haiku-5-5","output":{"fix":"- unknown","reach":"local","title":"libslirp: ICMP echo reply leaks host IP to guest","impact":"low","summary":"libslirp, the user-mode networking library used by QEMU and similar tools, mishandles ICMP echo replies when the normal ICMP socket is unavailable. A reply length mismatch leaks the host's real IP address to the guest, breaking NAT isolation.","category":"infrastructure","nicknames":[],"who_cares":["qemu","libslirp","self-hosted","virtualization"],"confidence":0.6,"needs_auth":"no","worst_case":"Guest learns the host's real IP address, weakening NAT isolation","analyst_note":"Find the fixed libslirp version and the upstream commit in the NVD entry (https://nvd.nist.gov/vuln/detail/CVE-2026-115449) and confirm which QEMU releases bundle the fix.","how_to_check":"- unknown","needs_analyst":true,"not_affected_if":["no-user-mode-networking","bridged-or-tap-networking"],"who_is_affected":"Systems that run guests on user-mode (SLIRP) networking through libslirp, such as QEMU guests using the default user networking backend, are the exposed case. Hosts that use bridged, tap or other non-SLIRP networking, or that do not run libslirp-based guests, can skip it. The sources do not say which libslirp versions are fixed.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"low"},"cost_usd":0.000597,"input_tokens":3351,"output_tokens":523,"severity_before":"low"},"analyst_status":null,"analyst_note":null,"search":"'-115449':12A,15A '-2026':11A,14A 'actual':84C 'address':57B,109C 'break':61B,120C 'caus':103C 'condit':92C 'cve':10A,13A 'data':85C 'echo':3A,38B,73C,118C 'expect':130C 'flaw':65C 'found':67C 'guest':9A,60B,115C 'handl':71C 'host':6A,21B,53B,89C,105C 'icmp':2A,37B,43B,72C,96C 'infrastructur':16B 'ip':7A,56B,108C 'isol':63B,123C 'leak':5A,51B,112C 'length':49B,77C,101C 'librari':29B 'libslirp':1A,17B,23B,69C 'match':82C 'mishandl':36B 'mismatch':50B,102C 'mode':27B,127C 'nat':62B,122C 'network':28B,128C 'normal':42B,95C 'provid':132C 'qemu':18B,32B 'real':55B,107C 'receiv':86C 'repli':4A,39B,48B,76C,119C 'request':74C 'self':20B 'self-host':19B 'similar':34B 'socket':44B,97C 'specif':91C 'tool':35B 'unavail':46B,99C 'updat':80C 'use':30B 'user':26B,126C 'user-mod':25B,125C 'virtual':22B","nicknames":[],"mitigations":[],"who_affected":"Systems that run guests on user-mode (SLIRP) networking through libslirp, such as QEMU guests using the default user networking backend, are the exposed case. Hosts that use bridged, tap or other non-SLIRP networking, or that do not run libslirp-based guests, can skip it. The sources do not say which libslirp versions are fixed.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-22T22:18:06+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N","cvss_by":"secalert@redhat.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-115449","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-115449","severity":null,"published_at":"2026-10-22T22:18:06+00:00","modified_at":"2026-10-23T16:44:17+00:00","first_seen_at":"2026-10-23T21:57:32+00:00","fetched_at":"2026-10-23T22:29:03+00:00","note":null},{"source":"epss","external_id":"CVE-2026-115449","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-115449","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T07:15:51+00:00","fetched_at":"2026-10-24T07:15:51+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"}