CVE-2026-72248 (GCVE-0-2026-72248)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:54 – Updated: 2026-08-17 05:41
VLAI
Title
netfilter: flowtable: support IPIP tunnel with direct xmit
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: flowtable: support IPIP tunnel with direct xmit The combination of IPIP tunnel with direct xmit, eg. bridge device, breaks because no dst_entry is provided to check the skb headroom and to set the iph->frag_off field. This leads to invalid dst usage and can trigger a crash in the tunnel transmit path. Fix this by moving dst_cache and dst_cookie out of the runtime union so that they can be shared by neighbour, xfrm, and direct tunnel flows. For FLOW_OFFLOAD_XMIT_DIRECT tuples carrying tunnel metadata, preserve route state in these shared fields and release it through the common dst release path. Since dst_entry is now available to the three supported xmit modes and dst_release() already deals with NULL dst, remove the xmit type check in nft_flow_dst_release(). Moreover, skip the check if the dst entry is NULL in nf_flow_dst_check() which is now the case for the direct xmit case. Based on patch from Rein Wei <n05ec@lzu.edu.cn>.
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d30301ba4b07ac92eb38353a111833b009003170 , < 0880c4ed122d0cddc9f29a2b28f055d1f24f0fca (git)
Affected: d30301ba4b07ac92eb38353a111833b009003170 , < fa7395c02d95e51bad2952325d2d6503bfbad437 (git)
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Linux Linux Affected: 6.19
Unaffected: 0 , < 6.19 (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/net/netfilter/nf_flow_table.h",
            "net/netfilter/nf_flow_table_core.c",
            "net/netfilter/nf_flow_table_ip.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "affected",
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              "versionType": "git"
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              "status": "affected",
              "version": "d30301ba4b07ac92eb38353a111833b009003170",
              "versionType": "git"
            }
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          "product": "Linux",
          "programFiles": [
            "include/net/netfilter/nf_flow_table.h",
            "net/netfilter/nf_flow_table_core.c",
            "net/netfilter/nf_flow_table_ip.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "status": "unaffected",
              "version": "0",
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              "status": "unaffected",
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          "nodes": [
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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              "negate": false,
              "operator": "OR"
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        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: flowtable: support IPIP tunnel with direct xmit\n\nThe combination of IPIP tunnel with direct xmit, eg. bridge device,\nbreaks because no dst_entry is provided to check the skb headroom and to\nset the iph-\u003efrag_off field. This leads to invalid dst usage and can\ntrigger a crash in the tunnel transmit path.\n\nFix this by moving dst_cache and dst_cookie out of the runtime union so\nthat they can be shared by neighbour, xfrm, and direct tunnel flows.\nFor FLOW_OFFLOAD_XMIT_DIRECT tuples carrying tunnel metadata, preserve\nroute state in these shared fields and release it through the common\ndst release path.\n\nSince dst_entry is now available to the three supported xmit modes and\ndst_release() already deals with NULL dst, remove the xmit type check\nin nft_flow_dst_release(). Moreover, skip the check if the dst entry\nis NULL in nf_flow_dst_check() which is now the case for the direct\nxmit case.\n\nBased on patch from Rein Wei \u003cn05ec@lzu.edu.cn\u003e."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bug is hit in the netfilter flowtable ingress fast path when remotely sourced TCP/UDP packets matching an offloaded flow are received on flowtable-bound interfaces, not via netlink configuration APIs.\nAC:L - An attacker can reliably establish the offloaded flow by sending matching traffic and then repeatedly trigger the faulty IPIP direct-xmit tunnel push on subsequent packets without depending on uncontrollable timing or memory layout.\nPR:N - Exploitation requires only the ability to send network traffic through an already deployed IPIP-through-bridge flowtable offload path; no local account, authentication, or CAP_NET_ADMIN on the target is needed to trigger the crash.\nUI:N - No victim interaction is required beyond normal network traffic delivery; the attacker does not need the user to open files, mount filesystems, or perform any deliberate action.\nS:U - Impact is confined to kernel memory corruption and denial of service on the affected network namespace/host; it does not cross a VM, container, or IOMMU security boundary to compromise a separate authority.\nC:H - FLOW_OFFLOAD_XMIT_DIRECT stores MAC/ifindex data in a union aliasing dst_cache, so nf_flow_tunnel_ipip_push dereferences attacker-influenced bytes as a dst_entry/rtable, enabling uncontrolled kernel memory reads before the fault.\nI:H - The same invalid dst pointer drives skb_cow_head/headroom calculations and tunnel header writes in kernel transmit context, giving a plausible path to heap corruption and control-flow disruption beyond a simple NULL dereference.\nA:H - Invalid dst usage in the IPIP tunnel transmit path can cause kernel oops/panic or hard lockup when offloaded flows are exercised, fully denying availability of the affected system."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:41:59.975Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
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          "url": "https://git.kernel.org/stable/c/0880c4ed122d0cddc9f29a2b28f055d1f24f0fca"
        },
        {
          "url": "https://git.kernel.org/stable/c/fa7395c02d95e51bad2952325d2d6503bfbad437"
        }
      ],
      "title": "netfilter: flowtable: support IPIP tunnel with direct xmit",
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  },
  "cveMetadata": {
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72248",
    "datePublished": "2026-08-15T05:54:36.535Z",
    "dateReserved": "2026-08-09T03:40:39.914Z",
    "dateUpdated": "2026-08-17T05:41:59.975Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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      "date": "2026-09-22",
      "epss": "0.00516",
      "percentile": "0.42944"
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                "programFiles": [
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                  "net/netfilter/nf_flow_table_core.c",
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                ],
                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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                "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
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        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: flowtable: support IPIP tunnel with direct xmit\n\nThe combination of IPIP tunnel with direct xmit, eg. bridge device,\nbreaks because no dst_entry is provided to check the skb headroom and to\nset the iph-\u003efrag_off field. This leads to invalid dst usage and can\ntrigger a crash in the tunnel transmit path.\n\nFix this by moving dst_cache and dst_cookie out of the runtime union so\nthat they can be shared by neighbour, xfrm, and direct tunnel flows.\nFor FLOW_OFFLOAD_XMIT_DIRECT tuples carrying tunnel metadata, preserve\nroute state in these shared fields and release it through the common\ndst release path.\n\nSince dst_entry is now available to the three supported xmit modes and\ndst_release() already deals with NULL dst, remove the xmit type check\nin nft_flow_dst_release(). Moreover, skip the check if the dst entry\nis NULL in nf_flow_dst_check() which is now the case for the direct\nxmit case.\n\nBased on patch from Rein Wei \u003cn05ec@lzu.edu.cn\u003e."
          }
        ],
        "id": "CVE-2026-72248",
        "lastModified": "2026-08-17T06:18:26.757",
        "metrics": {
          "cvssMetricV31": [
            {
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                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 9.8,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
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              "impactScore": 5.9,
              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-08-15T06:21:52.030",
        "references": [
          {
            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/0880c4ed122d0cddc9f29a2b28f055d1f24f0fca"
          },
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "url": "https://git.kernel.org/stable/c/fa7395c02d95e51bad2952325d2d6503bfbad437"
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
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      "current_release_date": "2026-08-17T14:55:16+00:00",
      "cve": "CVE-2026-72248",
      "id": "CVE-2026-72248",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "76",
      "product_status:known_not_affected": "198",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: netfilter: flowtable: support IPIP tunnel with direct xmit",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72248.json",
      "version": "3"
    },
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      "current_release_date": "2026-09-15T01:27:47Z",
      "cve": "CVE-2026-72248",
      "id": "CVE-2026-72248",
      "initial_release_date": "2026-08-21T00:42:13Z",
      "product_status:known_affected": "123",
      "product_status:known_not_affected": "239",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-72248",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-72248.json",
      "version": "5"
    }
  }
}



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