{"id":"CVE-2026-31665","title":"netfilter: nft_ct: fix use-after-free in timeout object destroy","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_ct: fix use-after-free in timeout object destroy\n\nnft_ct_timeout_obj_destroy() frees the timeout object with kfree()\nimmediately after nf_ct_untimeout(),…","severity":"high","cvss":7.8,"cvssVector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","cvssSource":"cna","vendor":"Linux","product":"Linux","affected":["Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < c458fc1c278a65ad5381083121d39a479973ebed","Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < c581e5c8f2b59158f62efe61c1a3dc36189081ff","Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < f16fe84879a5280f05ebbcea593a189ba0f3e79a","Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < 070abdf1b04325b21a20a2a0c39a2208af107275","Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < aa7cfa16f98f8ec3e6d47c34e1a8c1ae4b9b8b77","Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < b42aca3660dc2627a29a38131597ca610dc451f9","Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < d0983b48c10d1509fd795c155f8b1e832e1369ff","Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < f8dca15a1b190787bbd03285304b569631160eda","Linux 4.19"],"published":"2026-04-24","updated":"2026-09-08","sourceUpdated":"2026-09-08T08:47:57.476Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-31665","references":[{"url":"https://git.kernel.org/stable/c/c458fc1c278a65ad5381083121d39a479973ebed"},{"url":"https://git.kernel.org/stable/c/c581e5c8f2b59158f62efe61c1a3dc36189081ff"},{"url":"https://git.kernel.org/stable/c/f16fe84879a5280f05ebbcea593a189ba0f3e79a"},{"url":"https://git.kernel.org/stable/c/070abdf1b04325b21a20a2a0c39a2208af107275"},{"url":"https://git.kernel.org/stable/c/aa7cfa16f98f8ec3e6d47c34e1a8c1ae4b9b8b77"},{"url":"https://git.kernel.org/stable/c/b42aca3660dc2627a29a38131597ca610dc451f9"},{"url":"https://git.kernel.org/stable/c/d0983b48c10d1509fd795c155f8b1e832e1369ff"},{"url":"https://git.kernel.org/stable/c/f8dca15a1b190787bbd03285304b569631160eda"}],"tags":["cve.org"],"epss":0.00122,"epssPercentile":0.02306,"ingestedAt":"2026-09-08T15:33:26.990Z","slug":"CVE-2026-31665","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nft_ct: fix use-after-free in timeout object destroy\n\nnft_ct_timeout_obj_destroy() frees the timeout object with kfree()\nimmediately after nf_ct_untimeout(), without waiting for an RCU grace\nperiod. Concurrent packet processing on other CPUs may still hold\nRCU-protected references to the timeout object obtained via\nrcu_dereference() in nf_ct_timeout_data().\n\nAdd an rcu_head to struct nf_ct_timeout and use kfree_rcu() to defer\nfreeing until after an RCU grace period, matching the approach already\nused in nfnetlink_cttimeout.c.\n\nKASAN report:\n BUG: KASAN: slab-use-after-free in nf_conntrack_tcp_packet+0x1381/0x29d0\n Read of size 4 at addr ffff8881035fe19c by task exploit/80\n\n Call Trace:\n  nf_conntrack_tcp_packet+0x1381/0x29d0\n  nf_conntrack_in+0x612/0x8b0\n  nf_hook_slow+0x70/0x100\n  __ip_local_out+0x1b2/0x210\n  tcp_sendmsg_locked+0x722/0x1580\n  __sys_sendto+0x2d8/0x320\n\n Allocated by task 75:\n  nft_ct_timeout_obj_init+0xf6/0x290\n  nft_obj_init+0x107/0x1b0\n  nf_tables_newobj+0x680/0x9c0\n  nfnetlink_rcv_batch+0xc29/0xe00\n\n Freed by task 26:\n  nft_obj_destroy+0x3f/0xa0\n  nf_tables_trans_destroy_work+0x51c/0x5c0\n  process_one_work+0x2c4/0x5a0\n\n## Affected\n\n- `Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < c458fc1c278a65ad5381083121d39a479973ebed`\n- `Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < c581e5c8f2b59158f62efe61c1a3dc36189081ff`\n- `Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < f16fe84879a5280f05ebbcea593a189ba0f3e79a`\n- `Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < 070abdf1b04325b21a20a2a0c39a2208af107275`\n- `Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < aa7cfa16f98f8ec3e6d47c34e1a8c1ae4b9b8b77`\n- `Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < b42aca3660dc2627a29a38131597ca610dc451f9`\n- `Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < d0983b48c10d1509fd795c155f8b1e832e1369ff`\n- `Linux >= 7e0b2b57f01d183e1c84114f1f2287737358d748 < f8dca15a1b190787bbd03285304b569631160eda`\n- `Linux 4.19`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"twilight","depthScore":43,"depthScoreParts":{"impact":42.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}