{"id":"CVE-2026-99062","kind":"vulnerability","aliases":["CVE-2026-99062"],"related":[],"title":"Linux kernel: vsock read accounting bug breaks socket readiness reporting","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nvsock/virtio: account only unread bytes in read_skb()\n\nAfter a partial stream receive, rx_bytes tracks the unread suffix while\nbuf_used and peer credit still cover the whole packet.\nvirtio_transport_read_skb() dequeues that packet but passes pkt_len for\nboth counters, underflowing rx_bytes.\n\nOn a connected CID_LOCAL stream with an SK_SKB verdict, a 40-byte read\nfrom a 100-byte packet made SIOCINQ report -40, an empty recv return\nELOOP, and poll report the empty socket readable.  After verdict detach,\nreceiving 40 bytes wrapped the counter to zero and hid those queued bytes\nuntil one more byte arrived.  The fixed run kept the counter balanced\nand exposed all queued data immediately.\n\nThis was found during an LLM-assisted manual source audit of VSOCK\nreceive accounting while re-evaluating virtio_transport_read_skb() after\nCVE-2024-50169.\n\nSubtract only skb->len minus the VSOCK offset from rx_bytes.  Retain the\nfull packet length for buf_used and peer credit.","summary":"A bug in the Linux kernel's virtio vsock receive path subtracts the wrong byte count after a partial read, so the socket's pending-byte counter underflows. The sources describe wrong SIOCINQ values, false readable polls, and hidden queued data, with no sign of memory corruption or code execution.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["kernel","linux","runtime","virtio","vsock"],"not_affected_if":["no-sk-skb-verdict","no-vsock-use"],"how_to_check":"- unknown","fix":"- Update to a Linux kernel release that includes the upstream fix for 'vsock/virtio: account only unread bytes in read_skb()'; the sources do not name version numbers.","status":"open","published_at":"2026-10-23T13:17:30+00:00","first_seen_at":"2026-10-23T21:57:33+00:00","triaged_at":"2026-10-25T04:53:54+00:00","updated_at":"2026-10-25T04:53:54+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-25T04:53:54Z","model":"claude-haiku-5-5","output":{"fix":"- Update to a Linux kernel release that includes the upstream fix for 'vsock/virtio: account only unread bytes in read_skb()'; the sources do not name version numbers.","reach":"local","title":"Linux kernel: vsock read accounting bug breaks socket readiness reporting","impact":"low","summary":"A bug in the Linux kernel's virtio vsock receive path subtracts the wrong byte count after a partial read, so the socket's pending-byte counter underflows. The sources describe wrong SIOCINQ values, false readable polls, and hidden queued data, with no sign of memory corruption or code execution.","category":"runtime","nicknames":[],"who_cares":["linux","kernel","vsock","virtio"],"confidence":0.5,"needs_auth":"unknown","worst_case":"Socket byte counts go wrong and queued data stays hidden from readers","analyst_note":"Check the NVD entry and the upstream kernel commit for affected and fixed kernel versions, and for any distribution advisories.","how_to_check":"- unknown","needs_analyst":true,"not_affected_if":["no-vsock-use","no-sk-skb-verdict"],"who_is_affected":"Systems running a Linux kernel with virtio vsock and SK_SKB verdict programs on connected CID_LOCAL stream sockets are the ones described. The sources do not say which distributions or kernel versions are affected, and ordinary hosts without vsock sockets are unlikely to be exposed.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"low"},"cost_usd":0.000633,"input_tokens":3610,"output_tokens":544,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2024':225C '-2026':12A,15A '-40':153C '-50169':226C '-99062':13A,16A '100':147C '40':142C,170C 'account':5A,84C,214C 'arriv':186C 'assist':207C 'audit':210C 'balanc':193C 'break':7A 'buf':103C,244C 'bug':6A,23B 'byte':36B,48B,87C,97C,129C,143C,148C,171C,181C,185C,237C 'cid':133C 'code':71B 'connect':132C 'corrupt':69B 'count':37B 'counter':49B,126C,174C,192C 'cover':109C 'credit':107C,248C 'cve':11A,14A,224C 'data':63B,198C 'dequeu':117C 'describ':53B 'detach':168C 'eloop':158C 'empti':155C,163C 'evalu':218C 'execut':72B 'expos':195C 'fals':57B 'fix':188C 'follow':78C 'found':202C 'full':240C 'hid':178C 'hidden':61B 'immedi':199C 'kept':190C 'kernel':2A,17B,27B,76C 'len':123C,230C 'length':242C 'linux':1A,18B,26B,75C 'llm':206C 'llm-assist':205C 'local':134C 'made':150C 'manual':208C 'memori':68B 'minus':231C 'offset':234C 'one':183C 'packet':112C,119C,149C,241C 'partial':40B,93C 'pass':121C 'path':32B 'peer':106C,247C 'pend':47B 'pending-byt':46B 'pkt':122C 'poll':59B,160C 'queu':62B,180C,197C 're':217C 're-evalu':216C 'read':4A,41B,89C,115C,144C,221C 'readabl':58B,165C 'readi':9A 'receiv':31B,95C,169C,213C 'recv':156C 'report':10A,152C,161C 'resolv':82C 'retain':238C 'return':157C 'run':189C 'runtim':19B 'rx':96C,128C,236C 'sign':66B 'siocinq':55B,151C 'sk':138C 'skb':90C,116C,139C,222C,229C 'socket':8A,44B,164C 'sourc':52B,209C 'still':108C 'stream':94C,135C 'subtract':33B,227C 'suffix':101C 'track':98C 'transport':114C,220C 'underflow':50B,127C 'unread':86C,100C 'use':104C,245C 'valu':56B 'verdict':140C,167C 'virtio':20B,29B,113C,219C 'vsock':3A,21B,30B,212C,233C 'vsock/virtio':83C 'vulner':79C 'whole':111C 'wrap':172C 'wrong':35B,54B 'zero':176C","nicknames":[],"mitigations":[],"who_affected":"Systems running a Linux kernel with virtio vsock and SK_SKB verdict programs on connected CID_LOCAL stream sockets are the ones described. The sources do not say which distributions or kernel versions are affected, and ordinary hosts without vsock sockets are unlikely to be exposed.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-23T13:17:30+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-99062","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-99062","severity":null,"published_at":"2026-10-23T13:17:30+00:00","modified_at":"2026-10-23T13:17:30+00:00","first_seen_at":"2026-10-23T21:57:33+00:00","fetched_at":"2026-10-23T22:29:03+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"}