{"id":"CVE-2026-98574","kind":"vulnerability","aliases":["CVE-2026-98574"],"related":[],"title":"Linux kernel bcmgenet: transmit after ring free causes use-after-free","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnet: bcmgenet: stop Tx NAPI before disabling the queues\n\nbcmgenet_netif_stop() and the Wake-on-LAN branch of bcmgenet_suspend()\nboth disable the Tx queues first and stop Tx NAPI several steps later. A\ncompletion in flight calls netif_tx_wake_queue() in between, and nothing\nstops the queue again, so a transmit can reach the rings after they have\nbeen freed.\n\nClose is safe because dev_deactivate_many() stops the qdisc first.\nbcmgenet_suspend() does not, so stop Tx NAPI before the queues on both\npaths.\n\nKASAN on a Raspberry Pi CM4, driven from an MTU change because suspend\nfreezes user space before the callback runs:\n\n  BUG: KASAN: use-after-free in bcmgenet_xmit+0x17f8/0x2258\n  Write of size 8 at addr ffffff8055844a68 by task ksoftirqd/0/14\n   bcmgenet_xmit+0x17f8/0x2258\n   dev_hard_start_xmit+0x13c/0x588\n   sch_direct_xmit+0x108/0x340\n   __dev_queue_xmit+0x1190/0x3848","summary":"In the bcmgenet Ethernet driver, the Tx queues are disabled before Tx NAPI is stopped during close-less paths such as Wake-on-LAN suspend, so a completion can wake the queue and a transmit can write to freed rings. The sources show a KASAN use-after-free write in bcmgenet_xmit on a Raspberry Pi CM4, which can corrupt kernel memory.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["bcmgenet","infrastructure","linux-kernel","raspberry-pi","self-hosted"],"not_affected_if":["no-bcmgenet-hardware","other-nic-drivers"],"how_to_check":"- Run `uname -r` and compare against the fixed kernel in the sources, which the sources do not name\n- Check whether the machine uses the bcmgenet driver (Raspberry Pi 4 or CM4) with `lsmod | grep bcmgenet` or `ethtool -i eth0`\n- Check whether Wake-on-LAN is enabled with `ethtool eth0 | grep Wake`","fix":"- Update the Linux kernel to a release that includes the upstream commit for 'net: bcmgenet: stop Tx NAPI before disabling the queues' (version unknown from sources)\n- Until patched, unknown mitigation from sources","status":"open","published_at":"2026-10-18T16:17:09+00:00","first_seen_at":"2026-10-23T21:57:15+00:00","triaged_at":"2026-10-25T05:23:11+00:00","updated_at":"2026-10-25T05:23:11+00:00","category":"infrastructure","confidence":0.5,"triage":{"at":"2026-10-25T05:23:11Z","model":"claude-haiku-5-5","output":{"fix":"- Update the Linux kernel to a release that includes the upstream commit for 'net: bcmgenet: stop Tx NAPI before disabling the queues' (version unknown from sources)\n- Until patched, unknown mitigation from sources","reach":"local","title":"Linux kernel bcmgenet: transmit after ring free causes use-after-free","impact":"high","summary":"In the bcmgenet Ethernet driver, the Tx queues are disabled before Tx NAPI is stopped during close-less paths such as Wake-on-LAN suspend, so a completion can wake the queue and a transmit can write to freed rings. The sources show a KASAN use-after-free write in bcmgenet_xmit on a Raspberry Pi CM4, which can corrupt kernel memory.","category":"infrastructure","nicknames":[],"who_cares":["linux-kernel","raspberry-pi","bcmgenet","self-hosted"],"confidence":0.5,"needs_auth":"unknown","worst_case":"Kernel memory is written after free, possibly leading to crash or privilege escalation","analyst_note":"Find the fixed kernel version and upstream commit for the bcmgenet Tx NAPI fix, and confirm whether an unprivileged user can reach the path.","how_to_check":"- Run `uname -r` and compare against the fixed kernel in the sources, which the sources do not name\n- Check whether the machine uses the bcmgenet driver (Raspberry Pi 4 or CM4) with `lsmod | grep bcmgenet` or `ethtool -i eth0`\n- Check whether Wake-on-LAN is enabled with `ethtool eth0 | grep Wake`","needs_analyst":true,"not_affected_if":["other-nic-drivers","no-bcmgenet-hardware"],"who_is_affected":"Systems running a Linux kernel with the bcmgenet Ethernet driver, such as Raspberry Pi 4 and CM4 boards, are exposed, and the bug is reached through interface MTU changes and suspend with Wake-on-LAN enabled. Desktop or server machines with other NICs are not affected. The sources do not say whether a remote attacker can trigger the transmit path.","user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000763,"input_tokens":3650,"output_tokens":796,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'+0':223C,237C,243C,248C,253C '-2026':14A,17A '-98574':15A,18A '8':228C 'addr':230C 'bcmgenet':3A,19B,32B,83B,106C,114C,125C,180C,221C,235C 'branch':123C 'bug':214C 'call':144C 'callback':212C 'caus':8A 'chang':204C 'close':47B,169C 'close-less':46B 'cm4':89B,199C 'complet':59B,141C 'corrupt':92B 'cve':13A,16A 'deactiv':174C 'dev':173C,239C,250C 'direct':246C 'disabl':39B,111C,128C 'driven':200C 'driver':34B 'ethernet':33B 'ffffff8055844a68':231C 'first':132C,179C 'flight':143C 'follow':100C 'free':7A,12A,80B,219C 'freed':70B,168C 'freez':207C 'hard':240C 'host':29B 'infrastructur':20B 'kasan':76B,194C,215C 'kernel':2A,23B,93B,98C 'ksoftirqd/0/14':234C 'lan':55B,122C 'later':139C 'less':48B 'linux':1A,22B,97C 'linux-kernel':21B 'mani':175C 'memori':94B 'mtu':203C 'napi':42B,109C,136C,187C 'net':105C 'netif':115C,145C 'noth':152C 'path':49B,193C 'pi':26B,88B,198C 'qdisc':178C 'queue':37B,63B,113C,131C,148C,155C,190C,251C 'raspberri':25B,87B,197C 'raspberry-pi':24B 'reach':161C 'resolv':104C 'ring':6A,71B,163C 'run':213C 'safe':171C 'sch':245C 'self':28B 'self-host':27B 'sever':137C 'show':74B 'size':227C 'sourc':73B 'space':209C 'start':241C 'step':138C 'stop':44B,107C,116C,134C,153C,176C,185C 'suspend':56B,126C,181C,206C 'task':233C 'transmit':4A,66B,159C 'tx':36B,41B,108C,130C,135C,146C,186C 'use':10A,78B,217C 'use-after-fre':9A,77B,216C 'user':208C 'vulner':101C 'wake':53B,61B,120C,147C 'wake-on-lan':52B,119C 'write':68B,81B,225C 'x108/0x340':249C 'x1190/0x3848':254C 'x13c/0x588':244C 'x17f8/0x2258':224C,238C 'xmit':84B,222C,236C,242C,247C,252C","nicknames":[],"mitigations":[],"who_affected":"Systems running a Linux kernel with the bcmgenet Ethernet driver, such as Raspberry Pi 4 and CM4 boards, are exposed, and the bug is reached through interface MTU changes and suspend with Wake-on-LAN enabled. Desktop or server machines with other NICs are not affected. The sources do not say whether a remote attacker can trigger the transmit path.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-18T16:17:09+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-98574","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98574","severity":null,"published_at":"2026-10-18T16:17:09+00:00","modified_at":"2026-10-19T10:19:16+00:00","first_seen_at":"2026-10-23T21:57:15+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"}