CVE-2026-74695 (GCVE-0-2026-74695)
Vulnerability from cvelistv5
Published
2026-08-22 15:32
Modified
2026-08-25 05:41
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_flow_table: drop existing skb dst before skb_dst_set_noref() Incoming skbs passing through netfilter flowtable offload hooks (or XFRM offload path) might already carry a ref-counted dst_entry assigned during earlier RX or routing steps. Calling skb_dst_set_noref() when skb already holds a ref-counted dst overwrites skb->_skb_refdst, leaking the previous dst_entry reference count and triggering a DEBUG_NET_WARN_ON_ONCE assertion in skb_dst_check_unset(): WARNING: at skb_dst_check_unset include/linux/skbuff.h:1170 WARNING: at skb_dst_set_noref include/linux/skbuff.h:1234 WARNING: at nf_flow_offload_ip_hook+0xf6c/0x2b60 net/netfilter/nf_flow_table_ip.c:864 Drop any existing dst_entry reference with skb_dst_drop(skb) before setting the non-referenced flowtable destination.
Impacted products
Vendor Product Version
Linux Linux Version: 2a79fd3908acd88e6cb0e620c314d7b1fee56a02
Version: 2a79fd3908acd88e6cb0e620c314d7b1fee56a02
Version: 2a79fd3908acd88e6cb0e620c314d7b1fee56a02
Version: b4b1adf2e66ecc7125c4117e7aad9ff61e2cfd27
Version: 209dedf806d31095968f54323dbe62525b077b33
Version: 4.16.15   
Version: 4.17.1   
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_flow_table_ip.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
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              "versionType": "git"
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              "versionType": "git"
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            {
              "status": "affected",
              "version": "209dedf806d31095968f54323dbe62525b077b33",
              "versionType": "git"
            },
            {
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              "status": "affected",
              "version": "4.16.15",
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            },
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              "version": "4.17.1",
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            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_flow_table_ip.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.18"
            },
            {
              "lessThan": "4.18",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.45",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.9",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.45",
                  "versionStartIncluding": "4.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.9",
                  "versionStartIncluding": "4.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "4.18",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "4.16.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionStartIncluding": "4.17.1",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_flow_table: drop existing skb dst before skb_dst_set_noref()\n\nIncoming skbs passing through netfilter flowtable offload hooks (or XFRM\noffload path) might already carry a ref-counted dst_entry assigned during\nearlier RX or routing steps.\n\nCalling skb_dst_set_noref() when skb already holds a ref-counted dst\noverwrites skb-\u003e_skb_refdst, leaking the previous dst_entry reference\ncount and triggering a DEBUG_NET_WARN_ON_ONCE assertion in\nskb_dst_check_unset():\n\n  WARNING: at skb_dst_check_unset include/linux/skbuff.h:1170\n  WARNING: at skb_dst_set_noref include/linux/skbuff.h:1234\n  WARNING: at nf_flow_offload_ip_hook+0xf6c/0x2b60 net/netfilter/nf_flow_table_ip.c:864\n\nDrop any existing dst_entry reference with skb_dst_drop(skb) before\nsetting the non-referenced flowtable destination."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.5,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bug fires in nf_flow_offload_ip_hook on NF_NETDEV_INGRESS when remotely sourced IPv4/IPv6 packets matching an offloaded flow are received on nftables flowtable-bound interfaces, not via netlink configuration APIs.\nAC:L - Once a flowtable ingress hook and offloaded TCP/UDP flow exist, an attacker can reliably send matching traffic that reaches FLOW_OFFLOAD_XMIT_NEIGH or the XFRM offload path with a ref-counted skb dst; syzbot reproduced this without uncontrollable races.\nPR:N - Exploitation requires only sending network traffic through an already deployed nftables flow-offload path on an ingress device; no local account, authentication, or CAP_NET_ADMIN on the victim is needed to trigger the leak.\nUI:N - No victim interaction is required beyond normal network delivery; packets are processed automatically in softirq on the netdev ingress netfilter hook without opening files or mounting filesystems.\nS:U - Impact is confined to kernel refcount imbalance and availability degradation on the affected host; this is standard in-kernel compromise territory, not a VM escape, IOMMU bypass, or other cross-authority scope change.\nC:N - The flaw leaks a dst_entry reference by overwriting skb-\u003e_skb_refdst without releasing the prior dst; it does not expose kernel memory or provide an arbitrary read primitive.\nI:N - No unauthorized data modification occurs; the skb is forwarded using the intended flowtable destination while the previous dst reference is orphaned, not corrupted into a controllable write primitive.\nA:H - Each matching packet leaks a dst_entry refcount on the flowtable fast path, enabling sustained unauthenticated remote memory exhaustion on high-volume routers; CONFIG_DEBUG_NET builds also emit WARN_ON_ONCE during the overwrite."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-25T05:41:38.836Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/12afa450a6a6c0cce2c42b7545a9958f62d8a00c"
        },
        {
          "url": "https://git.kernel.org/stable/c/538e67e8c7889cf5f93951f5309d1bcb41f86036"
        },
        {
          "url": "https://git.kernel.org/stable/c/8aecf0bbcc72605592134c917c222207d8f63ab0"
        }
      ],
      "title": "netfilter: nf_flow_table: drop existing skb dst before skb_dst_set_noref()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74695",
    "datePublished": "2026-08-22T15:32:57.756Z",
    "dateReserved": "2026-08-15T05:44:03.926Z",
    "dateUpdated": "2026-08-25T05:41:38.836Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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  • Seen: The vulnerability was mentioned, discussed, or seen somewhere by the user.
  • Confirmed: The vulnerability is confirmed from an analyst perspective.
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