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

Vulnerability from cvelistv5 – Published: 2026-08-15 05:52 – Updated: 2026-08-23 12:46
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
Assigner
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)
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{
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          "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()."
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            "version": "3.1"
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              "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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    "dateReserved": "2026-08-09T03:40:39.903Z",
    "dateUpdated": "2026-08-23T12:46:36.427Z",
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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().\"}],\"affected\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"affectedData\":[{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"unaffected\",\"programFiles\":[\"net/sched/act_ct.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"0d76daf2013ce1da20eab5e26bd81d983e1c18fb\",\"lessThan\":\"fb080b6f54835d5d4d11ce3122800e6f0f6689e6\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ec624fe740b416fb68d536b37fb8eef46f90b5c2\",\"lessThan\":\"67d6b00a54446c008f52cf70fc0c2ad0c712f85d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ec624fe740b416fb68d536b37fb8eef46f90b5c2\",\"lessThan\":\"2400c4b05d58834b994500a9eec90a37db44187c\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ec624fe740b416fb68d536b37fb8eef46f90b5c2\",\"lessThan\":\"5c3ae5f6c7c6de73ea9b6a75154fe4ed343e1bac\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ec624fe740b416fb68d536b37fb8eef46f90b5c2\",\"lessThan\":\"b3d835407846134b0d54637c0281b39bebef831d\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ec624fe740b416fb68d536b37fb8eef46f90b5c2\",\"lessThan\":\"f7f45ceb855d9ba1cba594fb3f383255f7013fad\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"ec624fe740b416fb68d536b37fb8eef46f90b5c2\",\"lessThan\":\"9092e15defbe6c7bc241c306093ca9d358a578e7\",\"versionType\":\"git\",\"status\":\"affected\"},{\"version\":\"5.15.13\",\"lessThan\":\"5.15.217\",\"versionType\":\"semver\",\"status\":\"affected\"}]},{\"vendor\":\"Linux\",\"product\":\"Linux\",\"defaultStatus\":\"affected\",\"programFiles\":[\"net/sched/act_ct.c\"],\"repo\":\"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\"versions\":[{\"version\":\"5.16\",\"status\":\"affected\"},{\"version\":\"0\",\"lessThan\":\"5.16\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"5.15.217\",\"lessThanOrEqual\":\"5.15.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.1.184\",\"lessThanOrEqual\":\"6.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.6.145\",\"lessThanOrEqual\":\"6.6.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.12.97\",\"lessThanOrEqual\":\"6.12.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"6.18.40\",\"lessThanOrEqual\":\"6.18.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.1.5\",\"lessThanOrEqual\":\"7.1.*\",\"versionType\":\"semver\",\"status\":\"unaffected\"},{\"version\":\"7.2\",\"lessThanOrEqual\":\"*\",\"versionType\":\"original_commit_for_fix\",\"status\":\"unaffected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H\",\"baseScore\":8.2,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"LOW\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":3.9,\"impactScore\":4.2}]},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/2400c4b05d58834b994500a9eec90a37db44187c\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/5c3ae5f6c7c6de73ea9b6a75154fe4ed343e1bac\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/67d6b00a54446c008f52cf70fc0c2ad0c712f85d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/9092e15defbe6c7bc241c306093ca9d358a578e7\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/b3d835407846134b0d54637c0281b39bebef831d\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/f7f45ceb855d9ba1cba594fb3f383255f7013fad\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/fb080b6f54835d5d4d11ce3122800e6f0f6689e6\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}",
    "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"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.