CVE-2026-93138 (GCVE-0-2026-93138)
Vulnerability from cvelistv5
Published
2026-09-17 16:11
Modified
2026-10-19 09:06
Severity ?
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: Fix vmlinux BTF prep race in bpf_get_btf_vmlinux bpf_get_btf_vmlinux() lazily parses the vmlinux BTF under the bpf_verifier_lock, but publishes the result through a plain store and re-checks it through a plain lockless load. Nothing orders the stores initializing the struct btf inside btf_parse_vmlinux() against the store publishing the pointer: On a weakly ordered arch, a concurrent first-time caller taking the lockless fast path could in principle observe the pointer before the parsed contents are visible. The mutex_unlock() does not help such a reader given it only synchronizes with a later acquisition of the same lock. Thus, publish the pointer with smp_store_release() and read it on the fast path with smp_load_acquire(). Acquire semantics are needed rather than a dependency-ordered READ_ONCE(): btf_parse_vmlinux() also populates globals outside the returned object (e.g. bpf_ctx_convert.t). An address dependency would only order accesses performed through the pointer and not cover other globals.
References
Impacted products
Vendor Product Version
Linux Linux Version: 8580ac9404f6240668a026785d7d8856f0530409
Version: 8580ac9404f6240668a026785d7d8856f0530409
Version: 8580ac9404f6240668a026785d7d8856f0530409
Version: 8580ac9404f6240668a026785d7d8856f0530409
Version: 8580ac9404f6240668a026785d7d8856f0530409
Version: 8580ac9404f6240668a026785d7d8856f0530409
Version: 8580ac9404f6240668a026785d7d8856f0530409
Version: 8580ac9404f6240668a026785d7d8856f0530409
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{
  "containers": {
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        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/bpf/verifier.c"
          ],
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          "vendor": "Linux",
          "versions": [
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          "product": "Linux",
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          "vendor": "Linux",
          "versions": [
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            },
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              "version": "0",
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              "version": "7.2.6",
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              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
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              "cpeMatch": [
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                  "versionEndExcluding": "5.10.270",
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                  "versionEndExcluding": "7.3",
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              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: Fix vmlinux BTF prep race in bpf_get_btf_vmlinux\n\nbpf_get_btf_vmlinux() lazily parses the vmlinux BTF under the\nbpf_verifier_lock, but publishes the result through a plain store\nand re-checks it through a plain lockless load. Nothing orders\nthe stores initializing the struct btf inside btf_parse_vmlinux()\nagainst the store publishing the pointer: On a weakly ordered\narch, a concurrent first-time caller taking the lockless fast\npath could in principle observe the pointer before the parsed\ncontents are visible. The mutex_unlock() does not help such a\nreader given it only synchronizes with a later acquisition of the\nsame lock. Thus, publish the pointer with smp_store_release()\nand read it on the fast path with smp_load_acquire().\n\nAcquire semantics are needed rather than a dependency-ordered\nREAD_ONCE(): btf_parse_vmlinux() also populates globals outside\nthe returned object (e.g. bpf_ctx_convert.t). An address\ndependency would only order accesses performed through the\npointer and not cover other globals."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "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"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The race is reached from local bpf(2) BPF_PROG_LOAD: bpf_prog_load() calls bpf_get_btf_vmlinux() on the attach_btf_id path, and bpf_check() always calls it before verification. No remote protocol message carries the data that publishes btf_vmlinux.\nAC:L - The attacker issues concurrent BPF_PROG_LOAD (or BPF_MAP_CREATE of BPF_MAP_TYPE_STRUCT_OPS into bpf_struct_ops_map_alloc) so one thread runs btf_parse_vmlinux() under bpf_verifier_lock while the other takes the lockless `if (!btf_vmlinux)` load; they control both sides of that publication window.\nPR:L - The lockless consumer is bpf_check() when bpf_token_capable(token, CAP_BPF) sets is_priv and skips mutex_lock(\u0026bpf_verifier_lock). CAP_BPF is delegable with a BPF token into a non-init user namespace, so init-namespace root is not required.\nUI:N - The attacker issues the concurrent bpf(BPF_PROG_LOAD) or bpf(BPF_MAP_CREATE) syscalls themselves; no other user must mount a filesystem, open a file, or load a program.\nS:U - A torn struct btf and bpf_ctx_convert.t are consumed by the host verifier and BTF helpers in the same kernel; that is in-kernel privilege escalation or DoS, not a KVM/Xen guest-to-host escape or IOMMU bypass.\nC:H - A lockless reader can observe btf_vmlinux before btf-\u003etypes, btf-\u003estrings and btf-\u003ehdr.str_len are visible. btf_type_by_id() then returns btf-\u003etypes[id] and btf_str_by_offset() returns \u0026btf-\u003estrings[offset] (check_ptr_to_map_access, btf_find_by_name_kind), an unbounded kernel read.\nI:H - Privileged bpf_check() trusts that torn vmlinux BTF for PTR_TO_BTF_ID sizes, and get_kern_ctx_btf_id() walks bpf_ctx_convert.t members; garbage type metadata can accept illegal kernel stores. btf_get/btf_put on a not-yet-visible refcnt can also call_rcu btf_free_rcu of the live object.\nA:H - get_kern_ctx_btf_id() does btf_type_member(bpf_ctx_convert.t) with no NULL check when that global is still unseen, and check_ptr_to_map_access() loads t-\u003ename_off after btf_type_by_id() returns NULL because nr_types is still 0, oopsing the kernel."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-19T09:06:11.046Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f32a4a40bc635be25d6816da4bd91e9e58c31bf3"
        },
        {
          "url": "https://git.kernel.org/stable/c/a7fe72d780122eb934536f1719abad445f6afdf7"
        },
        {
          "url": "https://git.kernel.org/stable/c/e18a10b39c994f04e1ebd7f8fc042bb1ca8ad053"
        },
        {
          "url": "https://git.kernel.org/stable/c/978524ecfc1c539282df5858de1eec20748c6f74"
        },
        {
          "url": "https://git.kernel.org/stable/c/eaf302628a78806f66d8224d6ba03fb4d5025de4"
        },
        {
          "url": "https://git.kernel.org/stable/c/2892f3f44bf865c8fb6b6c0960edec4cc91806ee"
        },
        {
          "url": "https://git.kernel.org/stable/c/86d11c594d60b255b526fa5260f669463fb1a063"
        },
        {
          "url": "https://git.kernel.org/stable/c/92863e678070f57c17c868e4bfa2441a5c61ad2b"
        }
      ],
      "title": "bpf: Fix vmlinux BTF prep race in bpf_get_btf_vmlinux",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-93138",
    "datePublished": "2026-09-17T16:11:38.795Z",
    "dateReserved": "2026-09-17T16:02:15.088Z",
    "dateUpdated": "2026-10-19T09:06:11.046Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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