{"id":"CVE-2026-98703","kind":"vulnerability","aliases":["CVE-2026-98703"],"related":[],"title":"Linux kernel: wifi rate control debugfs write corrupts out-of-bounds memory","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nwifi: mac80211: minstrel_ht: validate fixed rate index\n\nThe fixed_rate_idx debugfs file is a plain u32 attribute, so any value\ncan be written to it.  minstrel_ht_update_stats() then copies the value\ninto mi->max_tp_rate[] and mi->max_prob_rate, and\nminstrel_ht_set_rate() uses MI_RATE_GROUP()/MI_RATE_IDX() to index\nminstrel_mcs_groups[] (42 entries) and mi->groups[].rates[] (10 entries)\nwith it.\n\nWriting e.g. 65535 selects group 4095 and rate index 15, far outside\nboth arrays.  The out-of-bounds entries are dereferenced and updated as\nstruct minstrel_rate_stats (retry counts, etc.), so the invalid index\ncorrupts adjacent kernel memory.  With CONFIG_UBSAN_BOUNDS the access is\nreported as an array-index-out-of-bounds in minstrel_ht_set_rate().\n\nOnly a valid group/rate pair, or U32_MAX to disable fixed rate\nprocessing, can be used safely, so reject any other value when the\ndebugfs file is written.\n\nThe file is only reachable through a root-only debugfs mount, so this is\nnot a privilege boundary.  The out-of-bounds access is still a bug that\nmust not be reachable through a writable debugfs attribute.","summary":"Writing an arbitrary value to the mac80211 minstrel_ht fixed_rate_idx debugfs file indexes arrays out of bounds, corrupting adjacent kernel memory. The file is only reachable through a root-only debugfs mount, so the impact is limited to a local user with root.","severity":"low","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["linux-kernel","mac80211","runtime","self-hosted","wifi"],"not_affected_if":["debugfs-not-mounted","default-config","no-wifi-hardware"],"how_to_check":"- Run `uname -r` and compare against the fixed kernel version in the sources (unknown)\n- Check whether a wifi driver using mac80211 is loaded with `lsmod | grep mac80211`\n- Check whether debugfs is mounted with `mount | grep debugfs`","fix":"- Update the Linux kernel to a release that includes the upstream commit validating the fixed rate index (version unknown from sources)","status":"open","published_at":"2026-10-18T16:17:23+00:00","first_seen_at":"2026-10-23T21:57:16+00:00","triaged_at":"2026-10-25T05:18:52+00:00","updated_at":"2026-10-25T05:18:52+00:00","category":"runtime","confidence":0.7,"triage":{"at":"2026-10-25T05:18:52Z","model":"claude-haiku-5-5","output":{"fix":"- Update the Linux kernel to a release that includes the upstream commit validating the fixed rate index (version unknown from sources)","reach":"local","title":"Linux kernel: wifi rate control debugfs write corrupts out-of-bounds memory","impact":"medium","summary":"Writing an arbitrary value to the mac80211 minstrel_ht fixed_rate_idx debugfs file indexes arrays out of bounds, corrupting adjacent kernel memory. The file is only reachable through a root-only debugfs mount, so the impact is limited to a local user with root.","category":"runtime","nicknames":[],"who_cares":["linux-kernel","wifi","mac80211","self-hosted"],"confidence":0.7,"needs_auth":"yes","worst_case":"local root user corrupts kernel memory via debugfs write","analyst_note":"Confirm the fixed kernel versions and stable backport commits from the NVD entry at https://nvd.nist.gov/vuln/detail/CVE-2026-98703.","how_to_check":"- Run `uname -r` and compare against the fixed kernel version in the sources (unknown)\n- Check whether a wifi driver using mac80211 is loaded with `lsmod | grep mac80211`\n- Check whether debugfs is mounted with `mount | grep debugfs`","needs_analyst":true,"not_affected_if":["no-wifi-hardware","debugfs-not-mounted","default-config"],"who_is_affected":"Only systems with a mac80211 wifi driver loaded and debugfs mounted, where the fixed_rate_idx file is writable by root. The sources say it is not a privilege boundary, so exposure matters mainly on shared or multi-user machines. Systems without wifi hardware or without mac80211 can skip it.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"low"},"cost_usd":0.000693,"input_tokens":3710,"output_tokens":645,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':15A,18A '-98703':16A,19A '/mi_rate_idx':139C '10':151C '15':164C '4095':160C '42':145C '65535':157C 'access':200C,268C 'adjac':49B,192C 'arbitrari':31B 'array':44B,168C,206C 'array-index-out-of-bound':205C 'attribut':103C,282C 'bound':12A,47B,173C,198C,210C,267C 'boundari':262C 'bug':272C 'config':196C 'control':5A 'copi':117C 'corrupt':8A,48B,191C 'count':185C 'cve':14A,17A 'debugf':6A,41B,62B,97C,240C,254C,281C 'dereferenc':176C 'disabl':225C 'e.g':156C 'entri':146C,152C,174C 'etc':186C 'far':165C 'file':42B,53B,98C,241C,245C 'fix':38B,90C,94C,226C 'follow':80C 'group':138C,144C,149C,159C 'group/rate':219C 'host':27B 'ht':37B,88C,113C,132C,213C 'idx':40B,96C 'impact':66B 'index':43B,92C,141C,163C,190C,207C 'invalid':189C 'kernel':2A,22B,50B,78C,193C 'limit':68B 'linux':1A,21B,77C 'linux-kernel':20B 'local':71B 'mac80211':23B,35B,86C 'max':122C,127C,223C 'mcs':143C 'memori':13A,51B,194C 'mi':121C,126C,136C,148C 'minstrel':36B,87C,112C,131C,142C,181C,212C 'mount':63B,255C 'must':274C 'out-of-bound':9A,170C,264C 'outsid':166C 'pair':220C 'plain':101C 'privileg':261C 'prob':128C 'process':228C 'rate':4A,39B,91C,95C,124C,129C,134C,137C,150C,162C,182C,215C,227C 'reachabl':56B,248C,277C 'reject':234C 'report':202C 'resolv':84C 'retri':184C 'root':60B,74B,252C 'root-on':59B,251C 'runtim':24B 'safe':232C 'select':158C 'self':26B 'self-host':25B 'set':133C,214C 'stat':115C,183C 'still':270C 'struct':180C 'tp':123C 'u32':102C,222C 'ubsan':197C 'updat':114C,178C 'use':135C,231C 'user':72B 'valid':89C,218C 'valu':32B,106C,119C,237C 'vulner':81C 'wifi':3A,28B,85C 'writabl':280C 'write':7A,29B,155C 'written':109C,243C","nicknames":[],"mitigations":[],"who_affected":"Only systems with a mac80211 wifi driver loaded and debugfs mounted, where the fixed_rate_idx file is writable by root. The sources say it is not a privilege boundary, so exposure matters mainly on shared or multi-user machines. Systems without wifi hardware or without mac80211 can skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-18T16:17:23+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-98703","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98703","severity":null,"published_at":"2026-10-18T16:17:23+00:00","modified_at":"2026-10-21T13:21:38+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"}