{"id":"CVE-2026-99027","kind":"vulnerability","aliases":["CVE-2026-99027"],"related":[],"title":"Linux kernel: team driver reuses freed packet buffer, crashing the kernel","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: team: stop reusing skb after queue override\n\nA nonzero dev_queue_xmit() result does not return ownership of the skb.\nWhen an override port's qdisc drops it, the queue override helper used to\ntry another port or the mode transmit op with the freed skb.\n\nReturn the handoff decision separately from transmit success. Select only\nthe first override port under RCU and stop after handing it the skb,\nregardless of the lower transmit result. Keep the existing success and\ndrop accounting.\n\n  BUG: KASAN: slab-use-after-free in sk_skb_reason_drop\n  Write of size 4 by task poc/5040\n  sk_skb_reason_drop (net/core/skbuff.c:1240)\n  dev_kfree_skb_any_reason (net/core/dev.c:3470)\n  ab_transmit (drivers/net/team/team_mode_activebackup.c:49)\n  team_xmit (drivers/net/team/team_core.c:1849)\n  __dev_direct_xmit (net/core/dev.c:4934)\n  Freed by task 5040:\n  __tcf_kfree_skb_list (net/sched/sch_generic.c:43)\n  __dev_queue_xmit (net/core/dev.c:4831)\n  team_xmit (drivers/net/team/team_core.c:1846)\n  Kernel panic - not syncing: KASAN: panic_on_warn set ...","summary":"The Linux kernel's team network driver kept using a packet buffer after the lower queue had already freed it, a use-after-free. The sources show a KASAN report with a kernel panic, and nothing on what an attacker can do beyond crashing the machine.","severity":"unknown","cvss":null,"epss":0.00209,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["linux-kernel","network-teaming","runtime","self-hosted"],"not_affected_if":["no-team-driver"],"how_to_check":"- Run `uname -r` and compare against the fixed kernel build listed by your distribution's advisory\n- Check whether the team driver is loaded with `lsmod | grep team`","fix":"- Update the Linux kernel to a build that includes the upstream commit 'net: team: stop reusing skb after queue override'; the sources do not list fixed version numbers","status":"open","published_at":"2026-10-23T13:17:25+00:00","first_seen_at":"2026-10-23T21:57:33+00:00","triaged_at":"2026-10-25T04:54:27+00:00","updated_at":"2026-10-25T12:38:50+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-25T04:54:27Z","model":"claude-haiku-5-5","output":{"fix":"- Update the Linux kernel to a build that includes the upstream commit 'net: team: stop reusing skb after queue override'; the sources do not list fixed version numbers","reach":"local","title":"Linux kernel: team driver reuses freed packet buffer, crashing the kernel","impact":"medium","summary":"The Linux kernel's team network driver kept using a packet buffer after the lower queue had already freed it, a use-after-free. The sources show a KASAN report with a kernel panic, and nothing on what an attacker can do beyond crashing the machine.","category":"runtime","nicknames":[],"who_cares":["linux-kernel","self-hosted","network-teaming"],"confidence":0.5,"needs_auth":"unknown","worst_case":"Kernel memory corruption causes a crash or panic on affected hosts","analyst_note":"Check the NVD entry and the kernel stable-tree commit for CVSS, fixed versions and whether unprivileged local users can reach the team transmit path.","how_to_check":"- Run `uname -r` and compare against the fixed kernel build listed by your distribution's advisory\n- Check whether the team driver is loaded with `lsmod | grep team`","needs_analyst":true,"not_affected_if":["no-team-driver"],"who_is_affected":"Systems that load the team driver (bonding-style link aggregation with team mode) and send traffic through an override port whose qdisc drops packets. Hosts that do not use team networking are unlikely to be exposed. The sources do not say whether unprivileged users can trigger it.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000652,"input_tokens":3691,"output_tokens":566,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':13A,16A '-99027':14A,17A '1240':192C '1846':231C '1849':207C '3470':199C '4':183C '43':222C '4831':227C '49':203C '4934':212C '5040':216C 'ab':200C 'account':167C 'alreadi':45B 'anoth':121C 'attack':68B 'beyond':71B 'buffer':8A,39B 'bug':168C 'crash':9A,72B 'cve':12A,15A 'decis':135C 'dev':95C,193C,208C,223C 'direct':209C 'driver':4A,34B 'drivers/net/team/team_core.c':206C,230C 'drivers/net/team/team_mode_activebackup.c':202C 'drop':112C,166C,179C,190C 'exist':163C 'first':143C 'follow':80C 'free':52B,174C 'freed':6A,46B,130C,213C 'hand':151C 'handoff':134C 'helper':117C 'host':27B 'kasan':57B,169C,236C 'keep':161C 'kept':35B 'kernel':2A,11A,20B,30B,61B,78C,232C 'kfree':194C,218C 'linux':1A,19B,29B,77C 'linux-kernel':18B 'list':220C 'lower':42B,158C 'machin':74B 'mode':125C 'net':85C 'net/core/dev.c':198C,211C,226C 'net/core/skbuff.c':191C 'net/sched/sch_generic.c':221C 'network':22B,33B 'network-team':21B 'nonzero':94C 'noth':64B 'op':127C 'overrid':92C,108C,116C,144C 'ownership':102C 'packet':7A,38B 'panic':62B,233C,237C 'poc/5040':186C 'port':109C,122C,145C 'qdisc':111C 'queue':43B,91C,96C,115C,224C 'rcu':147C 'reason':178C,189C,197C 'regardless':155C 'report':58B 'resolv':84C 'result':98C,160C 'return':101C,132C 'reus':5A,88C 'runtim':24B 'select':140C 'self':26B 'self-host':25B 'separ':136C 'set':240C 'show':55B 'size':182C 'sk':176C,187C 'skb':89C,105C,131C,154C,177C,188C,195C,219C 'slab':171C 'slab-use-after-fre':170C 'sourc':54B 'stop':87C,149C 'success':139C,164C 'sync':235C 'task':185C,215C 'tcf':217C 'team':3A,23B,32B,86C,204C,228C 'transmit':126C,138C,159C,201C 'tri':120C 'use':36B,50B,118C,172C 'use-after-fre':49B 'vulner':81C 'warn':239C 'write':180C 'xmit':97C,205C,210C,225C,229C","nicknames":[],"mitigations":[],"who_affected":"Systems that load the team driver (bonding-style link aggregation with team mode) and send traffic through an override port whose qdisc drops packets. Hosts that do not use team networking are unlikely to be exposed. The sources do not say whether unprivileged users can trigger it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-23T13:17:25+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-99027","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-99027","severity":null,"published_at":"2026-10-23T13:17:25+00:00","modified_at":"2026-10-23T13:17:25+00:00","first_seen_at":"2026-10-23T21:57:33+00:00","fetched_at":"2026-10-23T22:29:03+00:00","note":null},{"source":"epss","external_id":"CVE-2026-99027","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-99027","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-25T12:38:50+00:00","fetched_at":"2026-10-25T12:38:50+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"}