CVE-2026-89789 (GCVE-0-2026-89789)
Vulnerability from cvelistv5
Published
2026-09-16 08:48
Modified
2026-10-19 08:52
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: gtp: add synchronize_net() in gtp_newlink() error path to prevent use-after-free gtp_newlink()'s error path frees tid_hash and addr_hash without waiting for an RCU grace period after clearing sk_user_data. A concurrent gtp_encap_recv() in softirq may still hold the gtp_dev pointer obtained via rcu_dereference_sk_user_data() and access the freed memory. BUG: KASAN: slab-use-after-free in gtp0_pdp_find+0x1f6/0x200 (gtp.c:152) Call Trace: <IRQ> gtp0_pdp_find+0x1f6/0x200 gtp_encap_recv+0x527/0x24b0 udp_queue_rcv_one_skb+0x75f/0xc10 Add synchronize_net() before the kfree calls in out_hashtable, which covers all error paths from both gtp_encap_enable() and gtp_create_sockets().
References
Impacted products
Vendor Product Version
Linux Linux Version: 459aa660eb1d8ce67080da1983bb81d716aa5a69
Version: 459aa660eb1d8ce67080da1983bb81d716aa5a69
Version: 459aa660eb1d8ce67080da1983bb81d716aa5a69
Version: 459aa660eb1d8ce67080da1983bb81d716aa5a69
Version: 459aa660eb1d8ce67080da1983bb81d716aa5a69
Version: 459aa660eb1d8ce67080da1983bb81d716aa5a69
Version: 459aa660eb1d8ce67080da1983bb81d716aa5a69
Version: 459aa660eb1d8ce67080da1983bb81d716aa5a69
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "drivers/net/gtp.c"
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          "vendor": "Linux",
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          "vendor": "Linux",
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              "version": "6.12.110",
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              "version": "7.2.6",
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              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.270",
                  "versionStartIncluding": "4.7",
                  "vulnerable": true
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.157",
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                {
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                  "versionEndExcluding": "7.3",
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ngtp: add synchronize_net() in gtp_newlink() error path to prevent use-after-free\n\ngtp_newlink()\u0027s error path frees tid_hash and addr_hash without\nwaiting for an RCU grace period after clearing sk_user_data. A\nconcurrent gtp_encap_recv() in softirq may still hold the gtp_dev\npointer obtained via rcu_dereference_sk_user_data() and access the\nfreed memory.\n\n  BUG: KASAN: slab-use-after-free in gtp0_pdp_find+0x1f6/0x200 (gtp.c:152)\n  Call Trace:\n   \u003cIRQ\u003e\n   gtp0_pdp_find+0x1f6/0x200\n   gtp_encap_recv+0x527/0x24b0\n   udp_queue_rcv_one_skb+0x75f/0xc10\n\nAdd synchronize_net() before the kfree calls in out_hashtable, which\ncovers all error paths from both gtp_encap_enable() and\ngtp_create_sockets()."
        }
      ],
      "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"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The UAF is triggered from gtp_newlink()\u0027s RTM_NEWLINK error path (ip link add type gtp), a local rtnetlink configuration interface. Concurrent gtp_encap_recv() in softirq only uses already-freed tid_hash/addr_hash; a remote GTP-U peer cannot cause the free.\nAC:L - The attacker controls both sides of the RCU race: one thread issues RTM_NEWLINK that fails after setup_udp_tunnel_sock() (invalid second FD, IPv4/IPv6 family mismatch, or register_netdevice failure) while another floods UDP datagrams at the encap socket so gtp_encap_recv() still holds the gtp_dev pointer across the kfree.\nPR:L - Creating a GTP device requires CAP_NET_ADMIN in the target netns via rtnl_link_get_net_capable()/netlink_ns_capable(). Unprivileged users obtain this through user+network namespaces (unshare -Urn); gtp_link_ops has no extra init-namespace check and MODULE_ALIAS_RTNL_LINK(\"gtp\") permits module autoload.\nUI:N - The attacker opens its own UDP sockets, sends packets to them, and issues the failing RTM_NEWLINK from its own process. No separate victim action such as mounting a filesystem or opening a file is required.\nS:U - Impact is a host-kernel slab use-after-free in drivers/net/gtp.c, i.e. standard local privilege escalation within the same kernel security authority, not a KVM/Xen guest-to-host escape or IOMMU/DMA boundary bypass.\nC:H - gtp0_pdp_find()/gtp1_pdp_find() walk the attacker-sized freed tid_hash hlist under RCU. Heap spraying that slab yields a fake pdp_ctx and an arbitrary kernel read primitive, so Confidentiality is High per UAF guidance.\nI:H - A sprayed fake pdp_ctx is passed to gtp_rx(), which writes device stats, assigns skb-\u003edev, and calls __netif_rx(); combined with UAF heap reuse this is an arbitrary write and control-flow hijack primitive, so Integrity is High.\nA:H - KASAN reports slab-use-after-free in gtp0_pdp_find from gtp_encap_recv in softirq (udp_queue_rcv_one_skb). The UAF causes a kernel oops or panic even when not fully exploited, so Availability is High."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T08:52:43.083Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/fcafb2b1430824bae4258c01a439ec97ca0c6973"
        },
        {
          "url": "https://git.kernel.org/stable/c/3ca3da5c305caa873ddb81e8c6b118143f6dd3d1"
        },
        {
          "url": "https://git.kernel.org/stable/c/6f815c2fb6ab20385f81c353cdad0ea3b88132af"
        },
        {
          "url": "https://git.kernel.org/stable/c/e3b9aa0773abd5d4ed90be41ce5306c146d5b09e"
        },
        {
          "url": "https://git.kernel.org/stable/c/fd8396cfecbd904468c71362f08aaa25f96d5337"
        },
        {
          "url": "https://git.kernel.org/stable/c/7677eb2cbf2cc7446de474c01a6b06277c0051e5"
        },
        {
          "url": "https://git.kernel.org/stable/c/8d85498016a5bb56339734a14c276209fa65bafc"
        },
        {
          "url": "https://git.kernel.org/stable/c/d989e22ae9802c52c56ad4284d0caf26696cf6ae"
        }
      ],
      "title": "gtp: add synchronize_net() in gtp_newlink() error path to prevent use-after-free",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-89789",
    "datePublished": "2026-09-16T08:48:25.689Z",
    "dateReserved": "2026-09-11T19:38:34.766Z",
    "dateUpdated": "2026-10-19T08:52:43.083Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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