{"id":"CVE-2026-64525","state":"PUBLISHED","title":"xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit\n\nThe struct pernet_operations docstring in include/net/net_namespace.h\nexplicitly warns against blocking RCU primitives in .exit handlers:\n\n    Exit methods using blocking RCU primitives, such as\n    synchronize_rcu(), should be implemented via exit_batch.\n    [...]\n    Please, avoid synchronize_rcu() at all, where it's possible.\n\n    Note that a combination of pre_exit() and exit() can\n    be used, since a synchronize_rcu() is guaranteed between\n    the calls.\n\nxfrm_policy_fini() violates this: it calls synchronize_rcu() before\nfreeing the policy_bydst hash tables (so no RCU reader is mid-\ntraversal at free time), but runs from xfrm_net_ops.exit -- once per\nnamespace -- so a cleanup_net() of N namespaces pays N full RCU\ngrace periods serially.\n\nUse the documented pre_exit/exit split. Move the policy flush (and\nthe workqueue drains it depends on) into a new .pre_exit handler;\nxfrm_policy_fini() then runs in .exit and frees the hash tables\nafter the synchronize_rcu_expedited() that cleanup_net() guarantees\nbetween the two phases. Providing O(1) RCU grace periods per batch\ninstead of O(N).\n\nObserved on Linux 6.18 with a workload doing unshare(CLONE_NEWNET)\nat ~13/sec sustained: cleanup_net() and the netns_wq rescuer kthread\nboth stuck in xfrm_policy_fini()'s synchronize_rcu(), >300k struct\nnet accumulated in the cleanup queue, Percpu in /proc/meminfo climbed\nto 130+ GB on 256-CPU hosts, and memcg OOMs followed. setup_net and\n__put_net counts were balanced, ruling out a refcount leak.","publishedAt":"2026-07-25T09:20:49.256Z","updatedAt":"2026-10-30T12:27:58.969Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"438b1f668ad58f46ce699bb48e4698a7839e3f9e","status":"affected","lessThan":"bca6386dc08750fc7cdcbc7683473748ba3114b9","versionType":"git"},{"version":"3733fce2871c9bca9dd18a1a23b1432ea215a094","status":"affected","lessThan":"91cc13978ab0bc6f669139f53e7e613a860d10e0","versionType":"git"},{"version":"069daad4f2ae9c5c108131995529d5f02392c446","status":"affected","lessThan":"d14ae8ef88c2c6590e107db61b6adce148cec7b3","versionType":"git"},{"version":"069daad4f2ae9c5c108131995529d5f02392c446","status":"affected","lessThan":"3e52417318473782012b236d0325bf7d2266a597","versionType":"git"},{"version":"b2faee12538b5b008eaef65a4201eb29cb5cefb3","status":"affected","versionType":"git"},{"version":"b66920a3348c0f63ba18365248fa21fbf0b3a937","status":"affected","versionType":"git"},{"version":"33a3149dd81a1e2f52b80ee1e0fc380b39f3d028","status":"affected","versionType":"git"},{"version":"6.12.83","status":"affected","lessThan":"6.12.93","versionType":"semver"},{"version":"6.18.24","status":"affected","lessThan":"6.18.35","versionType":"semver"},{"version":"6.1.191","status":"affected","lessThan":"6.2","versionType":"semver"},{"version":"6.6.136","status":"affected","lessThan":"6.7","versionType":"semver"},{"version":"6.19.14","status":"affected","lessThan":"6.20","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/xfrm/xfrm_policy.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.0","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.35","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.12","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/xfrm/xfrm_policy.c"]}],"references":["https://git.kernel.org/stable/c/bca6386dc08750fc7cdcbc7683473748ba3114b9","https://git.kernel.org/stable/c/91cc13978ab0bc6f669139f53e7e613a860d10e0","https://git.kernel.org/stable/c/d14ae8ef88c2c6590e107db61b6adce148cec7b3","https://git.kernel.org/stable/c/3e52417318473782012b236d0325bf7d2266a597"],"weaknesses":[],"ingestedAt":"2026-10-30T12:46:06.359Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64525.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64525","state":"PUBLISHED","datePublished":"2026-07-25T09:20:49.256Z","dateUpdated":"2026-10-30T12:27:58.969Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T15:36:31.794Z"},"containers":{"cna":{"title":"xfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nxfrm: move policy_bydst RCU sync from per-netns .exit to .pre_exit\n\nThe struct pernet_operations docstring in include/net/net_namespace.h\nexplicitly warns against blocking RCU primitives in .exit handlers:\n\n    Exit methods using blocking RCU primitives, such as\n    synchronize_rcu(), should be implemented via exit_batch.\n    [...]\n    Please, avoid synchronize_rcu() at all, where it's possible.\n\n    Note that a combination of pre_exit() and exit() can\n    be used, since a synchronize_rcu() is guaranteed between\n    the calls.\n\nxfrm_policy_fini() violates this: it calls synchronize_rcu() before\nfreeing the policy_bydst hash tables (so no RCU reader is mid-\ntraversal at free time), but runs from xfrm_net_ops.exit -- once per\nnamespace -- so a cleanup_net() of N namespaces pays N full RCU\ngrace periods serially.\n\nUse the documented pre_exit/exit split. Move the policy flush (and\nthe workqueue drains it depends on) into a new .pre_exit handler;\nxfrm_policy_fini() then runs in .exit and frees the hash tables\nafter the synchronize_rcu_expedited() that cleanup_net() guarantees\nbetween the two phases. Providing O(1) RCU grace periods per batch\ninstead of O(N).\n\nObserved on Linux 6.18 with a workload doing unshare(CLONE_NEWNET)\nat ~13/sec sustained: cleanup_net() and the netns_wq rescuer kthread\nboth stuck in xfrm_policy_fini()'s synchronize_rcu(), >300k struct\nnet accumulated in the cleanup queue, Percpu in /proc/meminfo climbed\nto 130+ GB on 256-CPU hosts, and memcg OOMs followed. setup_net and\n__put_net counts were balanced, ruling out a refcount leak."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"438b1f668ad58f46ce699bb48e4698a7839e3f9e","status":"affected","lessThan":"bca6386dc08750fc7cdcbc7683473748ba3114b9","versionType":"git"},{"version":"3733fce2871c9bca9dd18a1a23b1432ea215a094","status":"affected","lessThan":"91cc13978ab0bc6f669139f53e7e613a860d10e0","versionType":"git"},{"version":"069daad4f2ae9c5c108131995529d5f02392c446","status":"affected","lessThan":"d14ae8ef88c2c6590e107db61b6adce148cec7b3","versionType":"git"},{"version":"069daad4f2ae9c5c108131995529d5f02392c446","status":"affected","lessThan":"3e52417318473782012b236d0325bf7d2266a597","versionType":"git"},{"version":"b2faee12538b5b008eaef65a4201eb29cb5cefb3","status":"affected","versionType":"git"},{"version":"b66920a3348c0f63ba18365248fa21fbf0b3a937","status":"affected","versionType":"git"},{"version":"33a3149dd81a1e2f52b80ee1e0fc380b39f3d028","status":"affected","versionType":"git"},{"version":"6.12.83","status":"affected","lessThan":"6.12.93","versionType":"semver"},{"version":"6.18.24","status":"affected","lessThan":"6.18.35","versionType":"semver"},{"version":"6.1.191","status":"affected","lessThan":"6.2","versionType":"semver"},{"version":"6.6.136","status":"affected","lessThan":"6.7","versionType":"semver"},{"version":"6.19.14","status":"affected","lessThan":"6.20","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/xfrm/xfrm_policy.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"7.0","status":"affected"},{"version":"0","status":"unaffected","lessThan":"7.0","versionType":"semver"},{"version":"6.12.93","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.35","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.0.12","status":"unaffected","lessThanOrEqual":"7.0.*","versionType":"semver"},{"version":"7.1","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["net/xfrm/xfrm_policy.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/bca6386dc08750fc7cdcbc7683473748ba3114b9"},{"url":"https://git.kernel.org/stable/c/91cc13978ab0bc6f669139f53e7e613a860d10e0"},{"url":"https://git.kernel.org/stable/c/d14ae8ef88c2c6590e107db61b6adce148cec7b3"},{"url":"https://git.kernel.org/stable/c/3e52417318473782012b236d0325bf7d2266a597"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:27:58.969Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.12.83","versionEndExcluding":"6.12.93"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.18.24","versionEndExcluding":"6.18.35"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.0","versionEndExcluding":"7.0.12"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.0","versionEndExcluding":"7.1"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.6.136"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19.14"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}