CVE-2026-72057 (GCVE-0-2026-72057)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:52 – Updated: 2026-10-19 21:19
VLAI
Title
net/sched: act_ct: preserve tc_skb_cb across defragmentation
Summary
In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: preserve tc_skb_cb across defragmentation tcf_ct_handle_fragments() calls nf_ct_handle_fragments() without saving and restoring skb->cb. The defrag helper clears IPCB/IP6CB, which aliases the tc_skb_cb/qdisc_skb_cb control buffer. Fragmented traffic through act_ct therefore loses qdisc metadata such as pkt_segs and can trigger WARN_ON_ONCE() in qdisc_pkt_segs() when panic_on_warn is enabled. Save and restore the full tc_skb_cb around nf_ct_handle_fragments(), matching the pattern used by ovs_ct_handle_fragments().
Severity
8.2 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 15:51 UTC
CWE
  • CWE-662 - Improper Synchronization
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6992 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 0d76daf2013ce1da20eab5e26bd81d983e1c18fb , < fb080b6f54835d5d4d11ce3122800e6f0f6689e6 (git)
Affected: ec624fe740b416fb68d536b37fb8eef46f90b5c2 , < 67d6b00a54446c008f52cf70fc0c2ad0c712f85d (git)
Affected: ec624fe740b416fb68d536b37fb8eef46f90b5c2 , < 2400c4b05d58834b994500a9eec90a37db44187c (git)
Affected: ec624fe740b416fb68d536b37fb8eef46f90b5c2 , < 5c3ae5f6c7c6de73ea9b6a75154fe4ed343e1bac (git)
Affected: ec624fe740b416fb68d536b37fb8eef46f90b5c2 , < b3d835407846134b0d54637c0281b39bebef831d (git)
Affected: ec624fe740b416fb68d536b37fb8eef46f90b5c2 , < f7f45ceb855d9ba1cba594fb3f383255f7013fad (git)
Affected: ec624fe740b416fb68d536b37fb8eef46f90b5c2 , < 9092e15defbe6c7bc241c306093ca9d358a578e7 (git)
Affected: 5.15.13 , < 5.15.217 (semver)
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Linux Linux Affected: 5.16
Unaffected: 0 , < 5.16 (semver)
Unaffected: 5.15.217 , ≤ 5.15.* (semver)
Unaffected: 6.1.184 , ≤ 6.1.* (semver)
Unaffected: 6.6.145 , ≤ 6.6.* (semver)
Unaffected: 6.12.97 , ≤ 6.12.* (semver)
Unaffected: 6.18.40 , ≤ 6.18.* (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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              {
                "lang": "en",
                "value": "CWE-662"
              }
            ],
            "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-17T19:07:50+00:00",
      "cve": "CVE-2026-72057",
      "id": "CVE-2026-72057",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "232",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: net/sched: act_ct: preserve tc_skb_cb across defragmentation",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72057.json",
      "version": "3"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-72057",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "yes"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-10-16T15:51:06.438816Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "problemTypes": [
              {
                "descriptions": [
                  {
                    "cweId": "CWE-662",
                    "description": "CWE-662 Improper Synchronization",
                    "lang": "en",
                    "type": "CWE"
                  }
                ]
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-10-16T15:51:07.134Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "defaultStatus": "unaffected",
              "product": "Linux",
              "programFiles": [
                "net/sched/act_ct.c"
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              "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",
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                  "versionType": "git"
                },
                {
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                  "status": "affected",
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                },
                {
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                  "versionType": "git"
                },
                {
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                  "status": "affected",
                  "version": "5.15.13",
                  "versionType": "semver"
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              ]
            },
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              "product": "Linux",
              "programFiles": [
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              ],
              "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
              "vendor": "Linux",
              "versions": [
                {
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                  "version": "5.16"
                },
                {
                  "lessThan": "5.16",
                  "status": "unaffected",
                  "version": "0",
                  "versionType": "semver"
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                  "status": "unaffected",
                  "version": "5.15.217",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.1.*",
                  "status": "unaffected",
                  "version": "6.1.184",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.6.*",
                  "status": "unaffected",
                  "version": "6.6.145",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.12.*",
                  "status": "unaffected",
                  "version": "6.12.97",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "6.18.*",
                  "status": "unaffected",
                  "version": "6.18.40",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "7.1.*",
                  "status": "unaffected",
                  "version": "7.1.5",
                  "versionType": "semver"
                },
                {
                  "lessThanOrEqual": "*",
                  "status": "unaffected",
                  "version": "7.2",
                  "versionType": "original_commit_for_fix"
                }
              ]
            }
          ],
          "cpeApplicability": [
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              "nodes": [
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                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "5.15.217",
                      "versionStartIncluding": "5.15.13",
                      "vulnerable": true
                    },
                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                      "versionEndExcluding": "6.1.184",
                      "versionStartIncluding": "5.16",
                      "vulnerable": true
                    },
                    {
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                      "versionEndExcluding": "6.6.145",
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                      "vulnerable": true
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                    {
                      "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                      "vulnerable": true
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                    {
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                  "negate": false,
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          ],
          "descriptions": [
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              "lang": "en",
              "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/sched: act_ct: preserve tc_skb_cb across defragmentation\n\ntcf_ct_handle_fragments() calls nf_ct_handle_fragments() without saving\nand restoring skb-\u003ecb. The defrag helper clears IPCB/IP6CB, which aliases\nthe tc_skb_cb/qdisc_skb_cb control buffer. Fragmented traffic through\nact_ct therefore loses qdisc metadata such as pkt_segs and can trigger\nWARN_ON_ONCE() in qdisc_pkt_segs() when panic_on_warn is enabled.\n\nSave and restore the full tc_skb_cb around nf_ct_handle_fragments(),\nmatching the pattern used by ovs_ct_handle_fragments()."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "baseScore": 8.2,
                "baseSeverity": "HIGH",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H",
                "version": "3.1"
              },
              "scenarios": [
                {
                  "lang": "en",
                  "value": "AV:N - The bug fires in tcf_ct_act() on the packet datapath (sch_handle_ingress/egress \u2192 tc_run \u2192 tcf_classify) when IP fragments arrive; on OVN/Kubernetes/SDN gateways and mlx5 offload nodes with act_ct already installed, a remote peer triggers it by sending fragmented traffic with no local access.\nAC:L - The attacker fully controls fragment boundaries and ordering; nf_ct_handle_fragments() memset of IPCB/IP6CB that aliases tc_skb_cb runs deterministically on each matching fragment through the configured ct action without races or memory-layout dependencies.\nPR:N - Installing act_ct requires CAP_NET_ADMIN, but triggering the bug on an already-configured internet-facing or tenant-facing gateway needs no target credentials; a remote attacker only sends crafted IP fragments, matching CNA precedent for packet-driven act_ct issues (e.g., CVE-2023-52610).\nUI:N - Exploitation requires only attacker-generated fragmented packets reaching a host with act_ct on clsact/ingress; no victim login, mount, or other interactive action is needed.\nS:U - WARN/panic and corrupted qdisc/tc metadata occur entirely within the host kernel security domain; this is not a VM escape, sandbox breakout, or IOMMU boundary bypass.\nC:N - memset(IPCB/IP6CB) zeroes tc_skb_cb/qdisc_skb_cb fields in place without out-of-bounds read or use-after-free; no kernel memory contents are disclosed to the attacker, only skb control-block metadata is clobbered.\nI:L - Clearing pkt_segs, pkt_len, post_ct, and zone corrupts tc/qdisc state consumed by bstats_update, sch_cake/sch_qfq, and cls_flower zone matching, enabling attacker-driven mis-accounting and mis-handling of packets on the affected path.\nA:H - Zeroed pkt_segs makes qdisc_pkt_segs() hit DEBUG_NET_WARN_ON_ONCE when it disagrees with GSO segment count; with panic_on_warn enabled this kernel-panics the host, and the condition is repeatable with sustained fragmented traffic."
                }
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            }
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            "dateUpdated": "2026-08-23T12:46:36.427Z",
            "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "shortName": "Linux"
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          "references": [
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              "url": "https://git.kernel.org/stable/c/fb080b6f54835d5d4d11ce3122800e6f0f6689e6"
            },
            {
              "url": "https://git.kernel.org/stable/c/67d6b00a54446c008f52cf70fc0c2ad0c712f85d"
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              "url": "https://git.kernel.org/stable/c/2400c4b05d58834b994500a9eec90a37db44187c"
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            },
            {
              "url": "https://git.kernel.org/stable/c/f7f45ceb855d9ba1cba594fb3f383255f7013fad"
            },
            {
              "url": "https://git.kernel.org/stable/c/9092e15defbe6c7bc241c306093ca9d358a578e7"
            }
          ],
          "title": "net/sched: act_ct: preserve tc_skb_cb across defragmentation",
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      "cveMetadata": {
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "assignerShortName": "Linux",
        "cveId": "CVE-2026-72057",
        "datePublished": "2026-08-15T05:52:12.873Z",
        "dateReserved": "2026-08-09T03:40:39.903Z",
        "dateUpdated": "2026-10-19T21:19:25.539Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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