CVE-2026-31665 (GCVE-0-2026-31665)
Vulnerability from cvelistv5
Published
2026-04-24 14:45
Modified
2026-04-27 14:04
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: nft_ct: fix use-after-free in timeout object destroy nft_ct_timeout_obj_destroy() frees the timeout object with kfree() immediately after nf_ct_untimeout(), without waiting for an RCU grace period. Concurrent packet processing on other CPUs may still hold RCU-protected references to the timeout object obtained via rcu_dereference() in nf_ct_timeout_data(). Add an rcu_head to struct nf_ct_timeout and use kfree_rcu() to defer freeing until after an RCU grace period, matching the approach already used in nfnetlink_cttimeout.c. KASAN report: BUG: KASAN: slab-use-after-free in nf_conntrack_tcp_packet+0x1381/0x29d0 Read of size 4 at addr ffff8881035fe19c by task exploit/80 Call Trace: nf_conntrack_tcp_packet+0x1381/0x29d0 nf_conntrack_in+0x612/0x8b0 nf_hook_slow+0x70/0x100 __ip_local_out+0x1b2/0x210 tcp_sendmsg_locked+0x722/0x1580 __sys_sendto+0x2d8/0x320 Allocated by task 75: nft_ct_timeout_obj_init+0xf6/0x290 nft_obj_init+0x107/0x1b0 nf_tables_newobj+0x680/0x9c0 nfnetlink_rcv_batch+0xc29/0xe00 Freed by task 26: nft_obj_destroy+0x3f/0xa0 nf_tables_trans_destroy_work+0x51c/0x5c0 process_one_work+0x2c4/0x5a0
References
Impacted products
Vendor Product Version
Linux Linux Version: 7e0b2b57f01d183e1c84114f1f2287737358d748
Version: 7e0b2b57f01d183e1c84114f1f2287737358d748
Version: 7e0b2b57f01d183e1c84114f1f2287737358d748
Version: 7e0b2b57f01d183e1c84114f1f2287737358d748
Version: 7e0b2b57f01d183e1c84114f1f2287737358d748
Version: 7e0b2b57f01d183e1c84114f1f2287737358d748
Version: 7e0b2b57f01d183e1c84114f1f2287737358d748
Version: 7e0b2b57f01d183e1c84114f1f2287737358d748
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/net/netfilter/nf_conntrack_timeout.h",
            "net/netfilter/nft_ct.c"
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          ],
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          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "0",
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              "version": "5.15.203",
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              "versionType": "original_commit_for_fix"
            }
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      "cpeApplicability": [
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              "negate": false,
              "operator": "OR"
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      ],
      "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": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-27T14:04:49.358Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "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"
        }
      ],
      "title": "netfilter: nft_ct: fix use-after-free in timeout object destroy",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
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  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31665",
    "datePublished": "2026-04-24T14:45:14.613Z",
    "dateReserved": "2026-03-09T15:48:24.129Z",
    "dateUpdated": "2026-04-27T14:04:49.358Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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