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CVE-2026-72423 (GCVE-0-2026-72423)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:56 – Updated: 2026-08-17 05:44
VLAI
Title
bpf: Guard conntrack opts error writes
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Guard conntrack opts error writes The conntrack lookup and allocation kfuncs take an opts pointer together with an opts__sz argument. The verifier checks only the memory range described by opts__sz, but the wrappers unconditionally write opts->error whenever the internal lookup or allocation helper returns an error. For an invalid size smaller than the end of opts->error, that write can land outside the verifier-checked range. Keep returning NULL for invalid arguments, but only report the error through opts->error when the supplied size includes the field. This preserves error reporting for the supported 12-byte and 16-byte layouts, and for other invalid sizes that still include opts->error.
Severity
8.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: b4c2b9593a1c4c3a718370e34af28e817fd5e5c6 , < dd74c80203842a21b2ebb9f70d1260d9aa20fa05 (git)
Affected: b4c2b9593a1c4c3a718370e34af28e817fd5e5c6 , < 6f6183a39533d727deaa5061cadae6dd9e6744d0 (git)
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Linux Linux Affected: 5.18
Unaffected: 0 , < 5.18 (semver)
Unaffected: 7.1.5 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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          "product": "Linux",
          "programFiles": [
            "net/netfilter/nf_conntrack_bpf.c"
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Guard conntrack opts error writes\n\nThe conntrack lookup and allocation kfuncs take an opts pointer\ntogether with an opts__sz argument. The verifier checks only the memory\nrange described by opts__sz, but the wrappers unconditionally write\nopts-\u003eerror whenever the internal lookup or allocation helper returns an\nerror.\n\nFor an invalid size smaller than the end of opts-\u003eerror, that write can\nland outside the verifier-checked range. Keep returning NULL for invalid\narguments, but only report the error through opts-\u003eerror when the\nsupplied size includes the field.\n\nThis preserves error reporting for the supported 12-byte and 16-byte\nlayouts, and for other invalid sizes that still include opts-\u003eerror."
        }
      ],
      "metrics": [
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
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              "value": "AV:L - Exploitation requires loading and attaching a BPF XDP or TC program that calls the conntrack kfuncs via the bpf() syscall; per kernel CNA guidance BPF/netfilter paths are Local even when programs later run on network packets.\nAC:L - An attacker reliably triggers the bug by calling bpf_xdp_ct_lookup/alloc or bpf_skb_ct_lookup/alloc with opts__sz smaller than the error field (e.g. 4); the helper returns EINVAL and the wrapper performs the out-of-bounds write with no races or attacker-uncontrollable conditions.\nPR:L - Loading BPF_PROG_TYPE_XDP or BPF_PROG_TYPE_SCHED_CLS programs requires CAP_NET_ADMIN, which unprivileged users can obtain inside user/network namespaces (unshare -Urn) on typical Linux deployments without init-namespace root.\nUI:N - No victim interaction is required; the attacker loads their own BPF program and invokes the kfunc with a small opts__sz to trigger the out-of-bounds write on demand.\nS:C - Corrupting kernel memory via a verifier-bypassing BPF stack write from a user/network namespace can cross the namespace/container trust boundary to compromise the host kernel, exceeding the attacker\u0027s original security scope.\nC:H - The bug is a controlled 4-byte out-of-bounds write past the verifier-approved opts buffer on the BPF stack, a memory-corruption primitive that can be leveraged for arbitrary kernel memory disclosure.\nI:H - Writing opts-\u003eerror outside the verifier-checked range corrupts adjacent BPF stack slots with attacker-influenced errno values, enabling heap/stack grooming and control-flow hijacking toward arbitrary kernel code execution.\nA:H - Corrupting BPF stack memory outside verifier bounds can cause immediate kernel oops/panic or be used in a repeatable crash/DoS loop when the attached XDP/TC program runs on incoming traffic."
            }
          ]
        }
      ],
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        "dateUpdated": "2026-08-17T05:44:03.898Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/dd74c80203842a21b2ebb9f70d1260d9aa20fa05"
        },
        {
          "url": "https://git.kernel.org/stable/c/6f6183a39533d727deaa5061cadae6dd9e6744d0"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72423",
    "datePublished": "2026-08-15T05:56:41.711Z",
    "dateReserved": "2026-08-09T03:40:39.928Z",
    "dateUpdated": "2026-08-17T05:44:03.898Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "date": "2026-09-04",
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      "percentile": "0.04839"
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      "version": "1"
    },
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    "redhat_vex": {
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      "current_release_date": "2026-08-18T07:28:07+00:00",
      "cve": "CVE-2026-72423",
      "id": "CVE-2026-72423",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "108",
      "product_status:known_not_affected": "166",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: bpf: Guard conntrack opts error writes",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72423.json",
      "version": "3"
    }
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}



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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.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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