{"id":"CVE-2026-99240","kind":"vulnerability","aliases":["CVE-2026-99240"],"related":[],"title":"Linux kernel: DAMON quota goal accepts zero target, risking division by zero","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/damon/core: error damos_commit_quota_goal() for zero target_value\n\nPatch series \"mm/damon: move zero damos quota target_value handling to the\ncore layer\".\n\nHaving zero DAMOS quota target value can cause division by zero.  DAMON\nAPI callers are checking the target value parameters to avoid that.  It is\neasy to make mistakes in some of the multiple API callers.  Move that to\nthe core layer.\n\nPatch 1 adds the corner case handling into the core layer DAMON parameters\nvalidation logic.  Patches 2 and 3 remove no more needed DAMON API callers\nside handling of the corner case in DAMON_LRU_SORT and DMON_SAMPLIE_MTIER,\nrespectively.\n\n\nThis patch (of 3):\n\nIf a DAMOS scheme has a damos_quota_goal of zero target_value,\ndamos_quota_goal() could trigger division-by-zero error.  Hence each DAMON\nAPI callers should do the zero target_value validation.  It is easy to\nmake mistakes.  Actually such bugs in DAMON_LRU_SORT and\nDAMON_SAMPLE_MTIER were found and fixed [1].\n\nIt is better to handle the corner case only once in the core layer,\ninstead of multiple places in all DAMON API callers.  One straightforward\noption is using an alternative denominator for the corner case in the\ndamos_quota_goal().  However, the zero target_value is meaningless.  In\nthis case, the quota goal is always evaluated as achieved or\nover-achieved.  The quota will only keep being reduced.\n\nSimply avoid using zero target_value by adding a check in the core layer\nDAMOS quota goal parameters validation/commit path,\ndamos_commit_quota_goal().  Update it to return an error in the case. \nAlso update its caller to propagate the error.","summary":"The Linux kernel's DAMON memory monitoring code could divide by zero when a DAMOS quota goal is set with a zero target value. The fix makes the core layer reject a zero target value instead of letting it reach the calculation.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["damon","linux-kernel","runtime"],"not_affected_if":["damon-unused"],"how_to_check":null,"fix":null,"status":"open","published_at":"2026-11-02T16:17:49+00:00","first_seen_at":"2026-11-02T16:24:06+00:00","triaged_at":"2026-11-02T16:26:48+00:00","updated_at":"2026-11-02T16:26:48+00:00","category":"runtime","confidence":0.4,"triage":{"at":"2026-11-02T16:26:48Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"local","title":"Linux kernel: DAMON quota goal accepts zero target, risking division by zero","impact":"low","summary":"The Linux kernel's DAMON memory monitoring code could divide by zero when a DAMOS quota goal is set with a zero target value. The fix makes the core layer reject a zero target value instead of letting it reach the calculation.","audience":"businesses","category":"runtime","nicknames":[],"who_cares":["linux-kernel","damon"],"confidence":0.4,"fix_status":"unknown","needs_auth":"unknown","worst_case":"unknown; a division-by-zero crash is the stated risk","analyst_note":"Check the kernel.org stable commit for affected version ranges and whether a non-root user can set DAMOS quota goals.","how_to_check":"unknown","plain_action":"","needs_analyst":true,"not_affected_if":["damon-unused"],"who_is_affected":"Affects Linux kernels that include the DAMON memory monitoring subsystem with DAMOS quota goals. The sources do not say which kernel versions are affected or whether the path is reachable by default, so teams should check their kernel version and whether DAMON is in use. Systems that do not use DAMON are likely unaffected.","user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"low"},"cost_usd":0.0007,"input_tokens":4642,"output_tokens":472,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':14A,17A '-99240':15A,18A '1':143C,243C '2':158C '3':160C,186C 'accept':6A 'achiev':301C,305C 'actual':228C 'add':144C,320C 'also':346C 'altern':273C 'alway':298C 'api':112C,134C,166C,213C,265C 'avoid':121C,314C 'better':246C 'bug':230C 'calcul':65B 'caller':113C,135C,167C,214C,266C,349C 'case':147C,173C,251C,278C,293C,345C 'caus':107C 'check':115C,322C 'code':31B 'commit':79C,334C 'core':52B,98C,140C,151C,256C,325C 'corner':146C,172C,250C,277C 'could':32B,203C 'cve':13A,16A 'damo':38B,78C,91C,102C,189C,193C,200C,281C,327C,333C 'damon':3A,19B,28B,111C,153C,165C,175C,212C,232C,236C,264C 'denomin':274C 'divid':33B 'divis':10A,108C,206C 'division-by-zero':205C 'dmon':179C 'easi':125C,224C 'error':77C,209C,342C,353C 'evalu':299C 'fix':49B,242C 'follow':71C 'found':240C 'goal':5A,40B,81C,195C,202C,283C,296C,329C,336C 'handl':95C,148C,169C,248C 'henc':210C 'howev':284C 'instead':59B,258C 'keep':310C 'kernel':2A,22B,26B,69C 'layer':53B,99C,141C,152C,257C,326C 'let':61B 'linux':1A,21B,25B,68C 'linux-kernel':20B 'logic':156C 'lru':176C,233C 'make':50B,127C,226C 'meaningless':290C 'memori':29B 'mistak':128C,227C 'mm/damon':88C 'mm/damon/core':76C 'monitor':30B 'move':89C,136C 'mtier':181C,238C 'multipl':133C,260C 'need':164C 'one':267C 'option':269C 'over-achiev':303C 'paramet':119C,154C,330C 'patch':86C,142C,157C,184C 'path':332C 'place':261C 'propag':351C 'quota':4A,39B,80C,92C,103C,194C,201C,282C,295C,307C,328C,335C 'reach':63B 'reduc':312C 'reject':54B 'remov':161C 'resolv':75C 'respect':182C 'return':340C 'risk':9A 'runtim':23B 'sampl':237C 'sampli':180C 'scheme':190C 'seri':87C 'set':42B 'side':168C 'simpli':313C 'sort':177C,234C 'straightforward':268C 'target':8A,46B,57B,84C,93C,104C,117C,198C,219C,287C,317C 'trigger':204C 'updat':337C,347C 'use':271C,315C 'valid':155C,221C 'validation/commit':331C 'valu':47B,58B,85C,94C,105C,118C,199C,220C,288C,318C 'vulner':72C 'zero':7A,12A,35B,45B,56B,83C,90C,101C,110C,197C,208C,218C,286C,316C","nicknames":[],"mitigations":[],"who_affected":"Affects Linux kernels that include the DAMON memory monitoring subsystem with DAMOS quota goals. The sources do not say which kernel versions are affected or whether the path is reachable by default, so teams should check their kernel version and whether DAMON is in use. Systems that do not use DAMON are likely unaffected.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"unknown","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["damon","linuxkernel","runtime","unknown"],"first_public_at":"2026-11-02T16:17:49+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-99240","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-99240","severity":null,"published_at":"2026-11-02T16:17:49+00:00","modified_at":"2026-11-02T16:17:49+00:00","first_seen_at":"2026-11-02T16:24:06+00:00","fetched_at":"2026-11-02T16:24:06+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"}