{"id":"CVE-2026-98788","title":"futex: Fix private hash use-after-free on resize","summary":"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 passe…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 56180dd20c19e5b0fa34822997a9ac66b517e7b3 < 5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af","Linux >= 56180dd20c19e5b0fa34822997a9ac66b517e7b3 < f35e3b5784221654f9cdbd6222275a7fa203f6c3","Linux 6.17"],"published":"2026-10-18","updated":"2026-10-18","sourceUpdated":"2026-10-18T15:48:24.833Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-98788","references":[{"url":"https://git.kernel.org/stable/c/5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af"},{"url":"https://git.kernel.org/stable/c/f35e3b5784221654f9cdbd6222275a7fa203f6c3"}],"tags":["cve.org"],"ingestedAt":"2026-10-18T16:47:32.487Z","slug":"CVE-2026-98788","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `Linux >= 56180dd20c19e5b0fa34822997a9ac66b517e7b3 < 5d5dc18b3a9ac011619b7d3af4514bf9e9b6a6af`\n- `Linux >= 56180dd20c19e5b0fa34822997a9ac66b517e7b3 < f35e3b5784221654f9cdbd6222275a7fa203f6c3`\n- `Linux 6.17`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}