CVE-2026-31665

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <libmnl/libmnl.h> #include <libnftnl/table.h> #include <libnftnl/obj.h> /* * PoC for CVE-2026-31665 (Conceptual) * This demonstrates the sequence to trigger the race condition. * Requires CAP_NET_ADMIN to manipulate nftables. */ int main() { struct mnl_socket *nl; struct nftnl_obj *obj; uint32_t portid, seq; // 1. Setup Netlink Socket nl = mnl_socket_open(NETLINK_NETFILTER); if (!nl) { perror("mnl_socket_open"); exit(EXIT_FAILURE); } // 2. Create a table and a timeout object printf("[*] Creating nftables table and timeout object...\n"); // Code to create table 'test_table' and obj 'test_timeout' would go here // using nftnl_obj_alloc() and batch sending. // 3. Trigger Traffic (Thread A) // Flood packets to ensure nf_conntrack_in is running on other CPUs printf("[*] Generating traffic to hold RCU references...\n"); // system("ping -f 127.0.0.1"); // 4. Destroy Object (Thread B - Main) // This calls nft_ct_timeout_obj_destroy() while traffic is active printf("[*] Deleting timeout object to trigger UAF...\n"); // Code to delete the object immediately. // If the timing is right, kfree() happens before RCU grace period ends. mnl_socket_close(nl); return 0; }

{"cve": {"id": "CVE-2026-31665", "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "published": "2026-04-24T15:16:46.157", "lastModified": "2026-04-27T20:00:05.430", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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(), 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"}], "metrics": {"cvssMetricV31": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH", "attackVector": "LOCAL", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 1.8, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-416"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.19.1", "versionEndExcluding": "5.10.253", "matchCriteriaId": "DCA68506-DA89-4BB0-BB51-9DE08D03AA32"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.11", "versionEndExcluding": "5.15.203", "matchCriteriaId": "20DDB3E9-AABF-4107-ADB0-5362AA067045"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.16", "versionEndExcluding": "6.1.169", "matchCriteriaId": "DBEC0E5D-641C-4E98-A6D9-5799B10CE451"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.2", "versionEndExcluding": "6.6.135", "matchCriteriaId": "15C1A1B2-14EE-494C-AF3E-D5A7BA640B39"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.7", "versionEndExcluding": "6.12.82", "matchCriteriaId": "02904CAE-71D2-45B3-9EC3-F6A9D18B6307"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.13", "versionEndExcluding": "6.18.23", "matchCriteriaId": "E9E09FDD-9EE3-4A56-92E2-2B30AFD0072F"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19", "versionEndExcluding": "6.19.13", "matchCriteriaId": "1490EF9B-9080-481C-8D22-1306AAE664E4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:4.19:-:*:*:*:*:*:*", "matchCriteriaId": "CFDAD450-8799-4C2D-80CE-2AA45DEC35CE"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc1:*:*:*:*:*:*", "matchCriteriaId": "F253B622-8837-4245-BCE5-A7BF8FC76A16"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc2:*:*:*:*:*:*", "matchCriteriaId": "4AE85AD8-4641-4E7C-A2F4-305E2CD9EE64"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc3:*:*:*:*:*:*", "matchCriteriaId": "F666C8D8-6538-46D4-B318-87610DE64C34"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc4:*:*:*:*:*:*", "matchCriteriaId": "02259FDA-961B-47BC-AE7F-93D7EC6E90C2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc5:*:*:*:*:*:*", "matchCriteriaId": "58A9FEFF-C040-420D-8F0A-BFDAAA1DF258"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc6:*:*:*:*:*:*", "matchCriteriaId": "1D2315C0-D46F-4F85-9754-F9E5E11374A6"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:7.0:rc7:*:*:*:*:*:*", "matchCriteriaId": "512EE3A8-A590-4501-9A94-5D4B268D6138"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/070abdf1b04325b21a20a2a0c39a2208af107275", "source": "416baaa9-dc9f-4396-8d5f-8c08 ... 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