CVE-2026-31665 (GCVE-0-2026-31665)

Vulnerability from cvelistv5 – Published: 2026-04-24 14:45 – Updated: 2026-04-24 14:45
VLAI?
Title
netfilter: nft_ct: fix use-after-free in timeout object destroy
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
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 7e0b2b57f01d183e1c84114f1f2287737358d748 , < c458fc1c278a65ad5381083121d39a479973ebed (git)
Affected: 7e0b2b57f01d183e1c84114f1f2287737358d748 , < c581e5c8f2b59158f62efe61c1a3dc36189081ff (git)
Affected: 7e0b2b57f01d183e1c84114f1f2287737358d748 , < f16fe84879a5280f05ebbcea593a189ba0f3e79a (git)
Affected: 7e0b2b57f01d183e1c84114f1f2287737358d748 , < 070abdf1b04325b21a20a2a0c39a2208af107275 (git)
Affected: 7e0b2b57f01d183e1c84114f1f2287737358d748 , < aa7cfa16f98f8ec3e6d47c34e1a8c1ae4b9b8b77 (git)
Affected: 7e0b2b57f01d183e1c84114f1f2287737358d748 , < b42aca3660dc2627a29a38131597ca610dc451f9 (git)
Affected: 7e0b2b57f01d183e1c84114f1f2287737358d748 , < d0983b48c10d1509fd795c155f8b1e832e1369ff (git)
Affected: 7e0b2b57f01d183e1c84114f1f2287737358d748 , < f8dca15a1b190787bbd03285304b569631160eda (git)
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    Linux Linux Affected: 4.19
Unaffected: 0 , < 4.19 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.169 , ≤ 6.1.* (semver)
Unaffected: 6.6.135 , ≤ 6.6.* (semver)
Unaffected: 6.12.82 , ≤ 6.12.* (semver)
Unaffected: 6.18.23 , ≤ 6.18.* (semver)
Unaffected: 6.19.13 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
            "include/net/netfilter/nf_conntrack_timeout.h",
            "net/netfilter/nft_ct.c"
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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"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-24T14:45:14.613Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/c458fc1c278a65ad5381083121d39a479973ebed"
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          "url": "https://git.kernel.org/stable/c/c581e5c8f2b59158f62efe61c1a3dc36189081ff"
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        },
        {
          "url": "https://git.kernel.org/stable/c/f8dca15a1b190787bbd03285304b569631160eda"
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      ],
      "title": "netfilter: nft_ct: fix use-after-free in timeout object destroy",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-31665",
    "datePublished": "2026-04-24T14:45:14.613Z",
    "dateReserved": "2026-03-09T15:48:24.129Z",
    "dateUpdated": "2026-04-24T14:45:14.613Z",
    "state": "PUBLISHED"
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      "date": "2026-04-25",
      "epss": "0.00024",
      "percentile": "0.06802"
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  }
}


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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



Detection rules are retrieved from Rulezet.