{"id":"CVE-2026-98788","state":"PUBLISHED","title":"futex: Fix private hash use-after-free on resize","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Fix private hash use-after-free on resize\n\npoll_state_synchronize_rcu(mm->futex.phash.batches) is used by\nfutex_ref_drop() to check that a grace period has passed since the\ncurrent hash was published. This relies on batches referencing a grace\nperiod which started after the hash pointer was assigned.\n\n__futex_pivot_hash() sets mmph->batches before it replaces mmph->hash:\n\n    scoped_guard(rcu) {\n            mmph->batches = get_state_synchronize_rcu();\n            rcu_assign_pointer(mmph->hash, new);\n    }\n\nThe scoped_guard(rcu) doesn't stop new grace periods from starting, and\nif one starts between those two assignments, futex_ref_drop() can move\nforward while a reader still holds a pointer to the old hash.\n\nFix things by setting mmph->batches after assigning mmph->hash.  The\nscoped_guard(rcu) isn't needed, so let's drop that as well.","publishedAt":"2026-10-18T15:48:24.833Z","updatedAt":"2026-10-19T09:25:41.209Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"56180dd20c19e5b0fa34822997a9ac66b517e7b3","status":"affected","lessThan":"5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af","versionType":"git"},{"version":"56180dd20c19e5b0fa34822997a9ac66b517e7b3","status":"affected","lessThan":"f35e3b5784221654f9cdbd6222275a7fa203f6c3","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/futex/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.17","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/futex/core.c"]}],"references":["https://git.kernel.org/stable/c/5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af","https://git.kernel.org/stable/c/f35e3b5784221654f9cdbd6222275a7fa203f6c3"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98788.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98788","state":"PUBLISHED","datePublished":"2026-10-18T15:48:24.833Z","dateUpdated":"2026-10-19T09:25:41.209Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.370Z"},"containers":{"cna":{"title":"futex: Fix private hash use-after-free on resize","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nfutex: Fix private hash use-after-free on resize\n\npoll_state_synchronize_rcu(mm->futex.phash.batches) is used by\nfutex_ref_drop() to check that a grace period has passed since the\ncurrent hash was published. This relies on batches referencing a grace\nperiod which started after the hash pointer was assigned.\n\n__futex_pivot_hash() sets mmph->batches before it replaces mmph->hash:\n\n    scoped_guard(rcu) {\n            mmph->batches = get_state_synchronize_rcu();\n            rcu_assign_pointer(mmph->hash, new);\n    }\n\nThe scoped_guard(rcu) doesn't stop new grace periods from starting, and\nif one starts between those two assignments, futex_ref_drop() can move\nforward while a reader still holds a pointer to the old hash.\n\nFix things by setting mmph->batches after assigning mmph->hash.  The\nscoped_guard(rcu) isn't needed, so let's drop that as well."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"56180dd20c19e5b0fa34822997a9ac66b517e7b3","status":"affected","lessThan":"5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af","versionType":"git"},{"version":"56180dd20c19e5b0fa34822997a9ac66b517e7b3","status":"affected","lessThan":"f35e3b5784221654f9cdbd6222275a7fa203f6c3","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/futex/core.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.17","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.17","versionType":"semver"},{"version":"7.2.10","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/futex/core.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af"},{"url":"https://git.kernel.org/stable/c/f35e3b5784221654f9cdbd6222275a7fa203f6c3"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:25:41.209Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.17","versionEndExcluding":"7.2.10"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.17","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}