CVE-2026-90317 (GCVE-0-2026-90317)

Vulnerability from cvelistv5 – Published: 2026-09-17 16:08 – Updated: 2026-09-18 17:54
VLAI
Title
bpf: Invalidate RCU pointers after final spin unlock
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Invalidate RCU pointers after final spin unlock In a sleepable BPF program, a spin lock can provide the only RCU protection for a kptr. The final bpf_spin_unlock() ends that protection, but the verifier leaves the pointer valid. Another CPU can then free the object before the pointer is used. A capability-limited runtime PoC triggered a task_struct use-after-free in __bpf_get_task_stack(). Record whether the program is in an RCU-protected context before releasing the lock. Invalidate RCU-protected pointers only when the unlock leaves the final such context. This preserves valid pointers in non-sleepable programs and inside an explicit RCU read-side section.
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: 5861d1e8dbc4e1a03ebffb96ac041026cdd34c07 , < 7ae71629357d0a6d0bdadb929c7b296d5b7e61c2 (git)
Affected: 5861d1e8dbc4e1a03ebffb96ac041026cdd34c07 , < 180c7000712db77063b3a26f4c97e7dd9038f449 (git)
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Linux Linux Affected: 6.6
Unaffected: 0 , < 6.6 (semver)
Unaffected: 7.2.6 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc1 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Invalidate RCU pointers after final spin unlock\n\nIn a sleepable BPF program, a spin lock can provide the only RCU protection\nfor a kptr. The final bpf_spin_unlock() ends that protection, but the\nverifier leaves the pointer valid. Another CPU can then free the object\nbefore the pointer is used. A capability-limited runtime PoC triggered a\ntask_struct use-after-free in __bpf_get_task_stack().\n\nRecord whether the program is in an RCU-protected context before releasing\nthe lock. Invalidate RCU-protected pointers only when the unlock leaves the\nfinal such context. This preserves valid pointers in non-sleepable programs\nand inside an explicit RCU read-side section."
        }
      ],
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            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
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              "lang": "en",
              "value": "AV:L - The attacker-controlled input is a sleepable BPF program loaded via bpf(BPF_PROG_LOAD) whose bytecode reaches process_spin_lock() in kernel/bpf/verifier.c, takes bpf_spin_lock, LDXes a map kptr, then bpf_spin_unlock. That program image arrives through the local bpf() syscall, not a network protocol message.\nAC:L - The attacker drives both sides: a sleepable fentry.s or BPF_PROG_TYPE_SYSCALL program loads a task kptr under bpf_spin_lock, unlocks, then uses it, while another thread bpf_kptr_xchg\u0027s the same slot to NULL so bpf_task_release_dtor/put_task_struct_rcu_user can call_rcu it. After unlock, preempt/IRQs are re-enabled so the grace period can finish; a PoC hit the UAF.\nPR:L - A sleepable BPF_PROG_TYPE_SYSCALL program is sufficient: bpf_prog_load() requires only bpf_token_capable(CAP_BPF) because is_perfmon_prog_type() is false for SYSCALL, and map_check_btf() needs CAP_BPF for BPF_SPIN_LOCK|BPF_KPTR fields. CAP_BPF is delegable via BPF tokens into a user namespace; the report used a capability-limited PoC, not init-namespace root.\nUI:N - The attacker loads the sleepable program, creates the lock+kptr ARRAY map, stores a task with bpf_task_from_pid/bpf_kptr_xchg, and runs it via bpf(BPF_PROG_TEST_RUN) (bpf_prog_test_run_syscall) or by calling getpgid after attaching fentry.s; no victim mount or file open is required.\nS:U - The use-after-free is of a host kernel task_struct consumed by bpf_task_acquire and __bpf_get_task_stack in the same kernel that accepted the program. That is local privilege escalation inside one kernel authority, not a VM, IOMMU, or guest-to-host crossing.\nC:H - After the final bpf_spin_unlock, process_spin_lock() leaves the map-loaded task kptr as MEM_RCU, so the program can LDX task_struct fields or call bpf_task_acquire (refcount_inc_not_zero on rcu_users) and __bpf_get_task_stack (try_get_task_stack/task_pt_regs) on a call_rcu-freed object. Spraying that slot yields an arbitrary kernel read.\nI:H - The same stale MEM_RCU task_struct pointer can be passed to bpf_task_acquire after bpf_task_release_dtor has dropped rcu_users and delayed_put_task_struct has freed it; a sprayed replacement becomes an owned kptr the attacker can feed to other kfuncs or store back with bpf_kptr_xchg, giving a write and control-flow primitive.\nA:H - Using the dangling task pointer in __bpf_get_task_stack (try_get_task_stack/task_pt_regs) or bpf_task_acquire after put_task_struct_rcu_user\u0027s call_rcu has run oopses or panics the kernel even without a full exploit."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-18T17:54:32.573Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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      "references": [
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          "url": "https://git.kernel.org/stable/c/7ae71629357d0a6d0bdadb929c7b296d5b7e61c2"
        },
        {
          "url": "https://git.kernel.org/stable/c/180c7000712db77063b3a26f4c97e7dd9038f449"
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      "title": "bpf: Invalidate RCU pointers after final spin unlock",
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    "cveId": "CVE-2026-90317",
    "datePublished": "2026-09-17T16:08:35.537Z",
    "dateReserved": "2026-09-11T19:38:34.801Z",
    "dateUpdated": "2026-09-18T17:54:32.573Z",
    "state": "PUBLISHED"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Invalidate RCU pointers after final spin unlock\n\nIn a sleepable BPF program, a spin lock can provide the only RCU protection\nfor a kptr. The final bpf_spin_unlock() ends that protection, but the\nverifier leaves the pointer valid. Another CPU can then free the object\nbefore the pointer is used. A capability-limited runtime PoC triggered a\ntask_struct use-after-free in __bpf_get_task_stack().\n\nRecord whether the program is in an RCU-protected context before releasing\nthe lock. Invalidate RCU-protected pointers only when the unlock leaves the\nfinal such context. This preserves valid pointers in non-sleepable programs\nand inside an explicit RCU read-side section."
          }
        ],
        "id": "CVE-2026-90317",
        "lastModified": "2026-09-18T18:17:53.437",
        "metrics": {
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                "attackVector": "LOCAL",
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                "baseSeverity": "HIGH",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
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              "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
              "type": "Secondary"
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        "published": "2026-09-17T17:17:29.580",
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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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.

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