CVE-2026-72427 (GCVE-0-2026-72427)

Vulnerability from cvelistv5 – Published: 2026-08-15 05:56 – Updated: 2026-08-17 05:44
VLAI
Title
bpf: Fix effective prog array index with BPF_F_PREORDER
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix effective prog array index with BPF_F_PREORDER replace_effective_prog() and purge_effective_progs() located the slot in the effective array by walking the program hlist and counting entries linearly. That count does not match the array layout: compute_effective_ progs() places BPF_F_PREORDER programs at the front (ancestor cgroup first, attach order within a cgroup) and the rest after them (descendant cgroup first). So when a preorder program is present, the linear hlist position no longer equals the program's index in the effective array. For replace_effective_prog() (bpf_link_update()) this overwrote the wrong slot, corrupting the effective order. For purge_effective_progs(), it could dummy out a slot belonging to a different program and leave the detached program in the array while bpf_prog_put() drops its reference, i.e. a use-after-free. Fix both by replaying compute_effective_progs()'s placement (including the per-cgroup preorder reversal) in a shared effective_prog_pos() helper. Identify the entry by its struct bpf_prog_list pointer rather than by (prog, link) value, so the lookup resolves to exactly the attachment the syscall selected even when the same bpf_prog is attached to several cgroups in the hierarchy.
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: bc8023ef3b11410682e5d4990e05e5bc2d3e1c94 , < 525e408c27ae714e538b8c608c3a974df3ab6c92 (git)
Affected: 555c0b713ca83968d3c843cb15485b9ba3367b1b , < 41b4320b84fdafe1ab586b06453d30d50415db59 (git)
Affected: 4b82b181a26cff8bf7adc3a85a88d121d92edeaf , < 9697db03e010391c55ae75192cbdf30c5a72c114 (git)
Affected: 4b82b181a26cff8bf7adc3a85a88d121d92edeaf , < b584f107ab90222bd825dcb4c5977326ff684109 (git)
Affected: 4b82b181a26cff8bf7adc3a85a88d121d92edeaf , < f08aaee3152d0dfc578b3f2586932d82062701dd (git)
Affected: 4707ad649cf662add3058bff47430817811b048d (git)
Affected: 6.6.93 , < 6.6.145 (semver)
Affected: 6.12.31 , < 6.12.97 (semver)
Affected: 6.14.9 , < 6.15 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 6.15
Unaffected: 0 , < 6.15 (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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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix effective prog array index with BPF_F_PREORDER\n\nreplace_effective_prog() and purge_effective_progs() located the slot in\nthe effective array by walking the program hlist and counting entries\nlinearly. That count does not match the array layout: compute_effective_\nprogs() places BPF_F_PREORDER programs at the front (ancestor cgroup\nfirst, attach order within a cgroup) and the rest after them (descendant\ncgroup first). So when a preorder program is present, the linear hlist\nposition no longer equals the program\u0027s index in the effective array.\n\nFor replace_effective_prog() (bpf_link_update()) this overwrote the\nwrong slot, corrupting the effective order. For purge_effective_progs(),\nit could dummy out a slot belonging to a different program and leave the\ndetached program in the array while bpf_prog_put() drops its reference,\ni.e. a use-after-free.\n\nFix both by replaying compute_effective_progs()\u0027s placement (including\nthe per-cgroup preorder reversal) in a shared effective_prog_pos()\nhelper. Identify the entry by its struct bpf_prog_list pointer rather\nthan by (prog, link) value, so the lookup resolves to exactly the\nattachment the syscall selected even when the same bpf_prog is attached\nto several cgroups in the hierarchy."
        }
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            "version": "3.1"
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              "value": "AV:L - Exploitation requires local bpf() syscalls (BPF_LINK_CREATE/BPF_PROG_ATTACH with BPF_F_PREORDER, BPF_LINK_UPDATE, BPF_PROG_DETACH/BPF_LINK_DETACH) through __cgroup_bpf_replace/__cgroup_bpf_detach in kernel/bpf/cgroup.c; per kernel CNA guidance BPF cgroup hooks are Local even when later triggered by packets.\nAC:L - Attacker fully controls cgroup hierarchy, BPF_F_PREORDER|BPF_F_ALLOW_MULTI attachments, and bpf_link_update/detach timing; purge_effective_progs UAF needs update_effective_progs() OOM which attacker can induce via memory pressure/large hierarchies, and bpf_link_update ordering corruption triggers without OOM.\nPR:L - Reaching the bug requires CAP_BPF (and CAP_NET_ADMIN for most cgroup BPF types) plus cgroup v2 attach access, commonly obtainable by unprivileged users via delegated cgroups or user namespaces (CAP_BPF/CAP_NET_ADMIN), not init-namespace root.\nUI:N - Attacker loads, attaches, and updates/detaches their own cgroup BPF programs and links via bpf(); no separate victim or administrator action is required.\nS:U - The bug corrupts kernel cgroup BPF effective-prog arrays causing UAF/ordering corruption within the same kernel security domain, enabling local privilege escalation rather than crossing VM, IOMMU, or sandbox boundaries.\nC:H - purge_effective_progs() can leave a detached bpf_prog pointer in the RCU-protected effective array while bpf_prog_put() frees it, yielding a use-after-free read when __cgroup_bpf_run_filter_* later executes the stale program under RCU.\nI:H - UAF of bpf_prog objects enables heap reuse for arbitrary kernel writes/control-flow hijack; bpf_link_update() mis-indexing can overwrite another attachment\u0027s effective slot so attacker-controlled BPF runs in place of security/filter programs on traffic for the whole cgroup tree.\nA:H - Freed-but-still-referenced programs are executed from softirq/network cgroup hooks and reliably cause kernel oops/panic/KASAN failures; ordering corruption can also crash or hang filtering paths serving container/cloud workloads."
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        "dateUpdated": "2026-08-17T05:44:07.623Z",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-72427",
    "datePublished": "2026-08-15T05:56:44.197Z",
    "dateReserved": "2026-08-09T03:40:39.928Z",
    "dateUpdated": "2026-08-17T05:44:07.623Z",
    "state": "PUBLISHED"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix effective prog array index with BPF_F_PREORDER\n\nreplace_effective_prog() and purge_effective_progs() located the slot in\nthe effective array by walking the program hlist and counting entries\nlinearly. That count does not match the array layout: compute_effective_\nprogs() places BPF_F_PREORDER programs at the front (ancestor cgroup\nfirst, attach order within a cgroup) and the rest after them (descendant\ncgroup first). So when a preorder program is present, the linear hlist\nposition no longer equals the program\u0027s index in the effective array.\n\nFor replace_effective_prog() (bpf_link_update()) this overwrote the\nwrong slot, corrupting the effective order. For purge_effective_progs(),\nit could dummy out a slot belonging to a different program and leave the\ndetached program in the array while bpf_prog_put() drops its reference,\ni.e. a use-after-free.\n\nFix both by replaying compute_effective_progs()\u0027s placement (including\nthe per-cgroup preorder reversal) in a shared effective_prog_pos()\nhelper. Identify the entry by its struct bpf_prog_list pointer rather\nthan by (prog, link) value, so the lookup resolves to exactly the\nattachment the syscall selected even when the same bpf_prog is attached\nto several cgroups in the hierarchy."
          }
        ],
        "id": "CVE-2026-72427",
        "lastModified": "2026-08-17T06:19:09.980",
        "metrics": {
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                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
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        "vulnStatus": "Received"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-18T15:16:47+00:00",
      "cve": "CVE-2026-72427",
      "id": "CVE-2026-72427",
      "initial_release_date": "2026-08-15T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: bpf: Fix effective prog array index with BPF_F_PREORDER",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-72427.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-02T11:45:42Z",
      "cve": "CVE-2026-72427",
      "id": "CVE-2026-72427",
      "initial_release_date": "2026-09-02T11:45:42Z",
      "product_status:known_not_affected": "362",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-72427",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-72427.json",
      "version": "2"
    }
  }
}



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