{"schema":"threatline.record/2","record":{"id":"CVE-2026-98284","aliases":[],"summary":"netlink: do not free nlk->groups while lockless readers can use it","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetlink: do not free nlk->groups while lockless readers can use it\n\nnetlink_realloc_groups() uses krealloc() under netlink_table_grab().\nWhenever NLGRPSZ(groups) lands in a different kmalloc bucket, the old\nbitmap is freed immediately.\n\nTwo readers of nlk->groups / nlk->ngroups do not hold the netlink\ntable lock:\n\n1) sk_diag_dump_groups(). Hashed (bound) sockets are dumped from the\n   rhashtable walk in __netlink_diag_dump(), which only holds RCU.\n   Only the mc_list part of the dump takes nl_table_lock.\n\n2) netlink_native_seq_show() (/proc/net/netlink), whose walk has been\n   lockless since commit 21e4902aea80 (\"netlink: Lockless lookup with\n   RCU grace period in socket release\").\n\nBoth can read a freed buffer, and sk_diag_dump_groups() can also read\npast the end of the old (smaller) buffer if it happens to load the old\n@groups pointer together with the new @ngroups value, copying the\nresult into a NETLINK_DIAG_GROUPS attribute.\n\nThis is the same class of bug that commit f773608026ee (\"netlink:\naccess nlk groups safely in netlink bind and getname\") fixed for bind()\nand getname(); these two readers were missed. Simply grabbing the table\nlock in sk_diag_dump_groups() is not an option, because it is also\ncalled with nl_table_lock already held from the mc_list section of the\ndump.\n\nMake the lockless readers safe instead:\n\n- Allocate a new bitmap and free the old one after an RCU grace period,\n  instead of relying on the implicit kfree() done by krealloc().\n\n- Publish @groups before @ngroups, both with release semantics, and have\n  the lockless readers load @ngroups first. A reader can then never pair\n  the new (bigger) size with the old (smaller) buffer, and a reader\n  picking up the new pointer while still seeing the old size is\n  guaranteed to see the initialized bitmap.\n\nnetlink_realloc_groups() is called from process context (bind() and\nsetsockopt()), so kfree_rcu_mightsleep() can be used, once the table\nhas been released.","categories":["Operating systems"],"product":"Linux","vendor":"Linux","ecosystem":null,"affected_ranges":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98284","source_modified_at":"2026-10-19T09:16:55.695Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"21e4902aea80ef35afc00ee8d2abdea4f519b7f7","lessThan":"22f313e211d58a66786c81487c3905fa5d4b2a8f","status":"affected","versionType":"git"},{"version":"21e4902aea80ef35afc00ee8d2abdea4f519b7f7","lessThan":"ceac0de741bfb47ca255eee075257b3bb31f0651","status":"affected","versionType":"git"}],"defaultStatus":"unaffected"},{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98284","source_modified_at":"2026-10-19T09:16:55.695Z","fetched_at":"2026-10-23T18:45:31.882637Z","product":"Linux","vendor":"Linux","versions":[{"version":"4.0","status":"affected"},{"version":"0","lessThan":"4.0","status":"unaffected","versionType":"semver"},{"version":"7.2.8","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3","lessThanOrEqual":"*","status":"unaffected","versionType":"original_commit_for_fix"}],"defaultStatus":"affected"}],"fixed_versions":[{"source":"CVE List","source_url":"https://www.cve.org/CVERecord?id=CVE-2026-98284","source_modified_at":"2026-10-19T09:16:55.695Z","fetched_at":"2026-10-23T18:45:31.882637Z","package":{"name":"Linux","ecosystem":null},"version":"22f313e211d58a66786c81487c3905fa5d4b2a8f","basis":"first unaffected version stated in the CVE record"}],"cvss":null,"severity":null,"kev":{"listed":false},"epss":{"probability":0.00162,"percentile":0.05093,"score_date":"2026-10-23"},"published_at":"2026-10-06T08:45:45.443Z","modified_at":"2026-10-19T09:16:55.695Z","provenance":[{"source":"CVE List","url":"https://www.cve.org/CVERecord?id=CVE-2026-98284","fetched_at":"2026-10-23T18:45:31.882637Z","source_modified_at":"2026-10-19T09:16:55.695Z"},{"source":"EPSS","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-98284","fetched_at":"2026-10-23T18:42:43.628194Z","source_modified_at":"2026-10-23"}],"sources":["CVE List","EPSS"],"references":[{"source":"CVE List","url":"https://git.kernel.org/stable/c/22f313e211d58a66786c81487c3905fa5d4b2a8f"},{"source":"CVE List","url":"https://git.kernel.org/stable/c/ceac0de741bfb47ca255eee075257b3bb31f0651"}],"locations":[],"motoko_assessment":{"status":"requires_architecture_review","automatic_remediation":false},"cve_state":"PUBLISHED","classification":{"method":"product-first software-layer rules","rules_version":"2.1","matched_on":"product","confidence":"heuristic","reviewed":false},"change_timestamp":"2026-10-19T09:16:55.695Z","content_hash":"be407e7a584980385f63e2a695a6ebc6ad8345dc096b9f519b1220197fc8f844"}}