{"id":"CVE-2026-98625","kind":"vulnerability","aliases":["CVE-2026-98625"],"related":[],"title":"Linux kernel: flowtable offload worker can cause use-after-free","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: flowtable: publish HW_DEAD after worker is done\n\nflow_offload_work_del() sets NF_FLOW_HW_DEAD before the work handler\nclears NF_FLOW_HW_PENDING. Once a flow is both HW_DYING and HW_DEAD, a\nconcurrent garbage collection pass can remove it and schedule it for RCU\nfreeing.\n\nThe offload worker holds neither an RCU read lock nor a reference to the\nflow. If it is preempted after publishing HW_DEAD, the RCU callback can\nfree the flow before the worker resumes and clears HW_PENDING, resulting\nin a use-after-free.\n\nMove HW_DEAD publication to the common worker epilogue after the pending\nbit is cleared, making it the final flow access by destroy work. Order all\npreceding flow accesses before publishing the bit that allows garbage\ncollection to free the object.","summary":"In the Linux netfilter flowtable code, a flow can be marked dead before the offload worker finishes with it, so garbage collection may free it while the worker still uses it. The sources describe this as a use-after-free, which can lead to a crash or memory corruption in the kernel.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["linux-kernel","netfilter","nftables","runtime","self-hosted"],"not_affected_if":["no-flowtable-configured"],"how_to_check":"- `uname -r` to see the running kernel version\n- Check whether the flowtable feature is in use: `nft list ruleset | grep -i flowtable`\n- unknown for the exact vulnerable version range","fix":"- Update the Linux kernel to a release that includes the upstream netfilter flowtable fix (version unknown from sources)\n- Reboot after installing the patched kernel","status":"open","published_at":"2026-10-18T16:17:15+00:00","first_seen_at":"2026-10-23T21:57:16+00:00","triaged_at":"2026-10-25T05:21:11+00:00","updated_at":"2026-10-25T05:21:11+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-25T05:21:11Z","model":"claude-haiku-5-5","output":{"fix":"- Update the Linux kernel to a release that includes the upstream netfilter flowtable fix (version unknown from sources)\n- Reboot after installing the patched kernel","reach":"local","title":"Linux kernel: flowtable offload worker can cause use-after-free","impact":"high","summary":"In the Linux netfilter flowtable code, a flow can be marked dead before the offload worker finishes with it, so garbage collection may free it while the worker still uses it. The sources describe this as a use-after-free, which can lead to a crash or memory corruption in the kernel.","category":"runtime","nicknames":[],"who_cares":["linux-kernel","netfilter","nftables","self-hosted"],"confidence":0.5,"needs_auth":"unknown","worst_case":"kernel memory is freed early and reused, enabling crashes or code execution","analyst_note":"Find the affected and fixed kernel version ranges and the upstream commit from the NVD entry or kernel.org stable mailing list; confirm whether the flaw is reachable remotely.","how_to_check":"- `uname -r` to see the running kernel version\n- Check whether the flowtable feature is in use: `nft list ruleset | grep -i flowtable`\n- unknown for the exact vulnerable version range","needs_analyst":true,"not_affected_if":["no-flowtable-configured"],"who_is_affected":"Systems running the Linux kernel with netfilter flowtable offload configured, typically routers, firewalls and gateways that use nftables flow offload. Hosts that do not configure flowtables are unlikely to be exposed. The sources do not say which kernel versions are affected.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"unknown"},"cost_usd":0.000652,"input_tokens":3534,"output_tokens":597,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':13A,16A '-98625':14A,17A 'access':206C,214C 'allow':220C 'bit':198C,218C 'callback':166C 'caus':7A 'clear':112C,176C,200C 'code':32B 'collect':48B,130C,222C 'common':192C 'concurr':128C 'corrupt':76B 'crash':73B 'cve':12A,15A 'dead':38B,94C,107C,126C,163C,188C 'del':102C 'describ':60B 'destroy':208C 'die':123C 'done':98C 'epilogu':194C 'final':204C 'finish':43B 'flow':34B,99C,105C,114C,119C,155C,170C,205C,213C 'flowtabl':3A,31B,91C 'follow':85C 'free':11A,50B,67B,140C,168C,185C,224C 'garbag':47B,129C,221C 'handler':111C 'hold':144C 'host':26B 'hw':93C,106C,115C,122C,125C,162C,177C,187C 'kernel':2A,20B,79B,83C 'lead':70B 'linux':1A,19B,29B,82C 'linux-kernel':18B 'lock':149C 'make':201C 'mark':37B 'may':49B 'memori':75B 'move':186C 'neither':145C 'netfilt':21B,30B,90C 'nf':104C,113C 'nftabl':22B 'object':226C 'offload':4A,41B,100C,142C 'order':210C 'pass':131C 'pend':116C,178C,197C 'preced':212C 'preempt':159C 'public':189C 'publish':92C,161C,216C 'rcu':139C,147C,165C 'read':148C 'refer':152C 'remov':133C 'resolv':89C 'result':179C 'resum':174C 'runtim':23B 'schedul':136C 'self':25B 'self-host':24B 'set':103C 'sourc':59B 'still':55B 'use':9A,56B,65B,183C 'use-after-fre':8A,64B,182C 'vulner':86C 'work':101C,110C,209C 'worker':5A,42B,54B,96C,143C,173C,193C","nicknames":[],"mitigations":[],"who_affected":"Systems running the Linux kernel with netfilter flowtable offload configured, typically routers, firewalls and gateways that use nftables flow offload. Hosts that do not configure flowtables are unlikely to be exposed. The sources do not say which kernel versions are affected.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-18T16:17:15+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-98625","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98625","severity":null,"published_at":"2026-10-18T16:17:15+00:00","modified_at":"2026-10-19T10:19:26+00:00","first_seen_at":"2026-10-23T21:57:16+00:00","fetched_at":"2026-10-23T22:28:56+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"}