CVE-2026-74590 (GCVE-0-2026-74590)

Vulnerability from cvelistv5 – Published: 2026-08-22 15:31 – Updated: 2026-08-25 05:40
VLAI
Title
fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions
Summary
In the Linux kernel, the following vulnerability has been resolved: fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions The BPF verifier and the dynptr abstraction ensure that the memory space referenced by a dynptr remains valid. They do not, however, provide any guarantee that the contents of the memory are stable. kfuncs are expected to remain memory-safe even if concurrent modifications occur. bpf_get_fsverity_digest() didn't follow that: it could crash if arg->digest_size was concurrently modified. Fix that by using the known-good value hash_alg->digest_size instead. Also widen 'dynptr_sz' and 'out_digest_sz' to u64 to match the return type of __bpf_dynptr_size(). It doesn't appear that it can actually be more than INT_MAX currently (since __bpf_dynptr_data_rw() excludes file-based pointers), but the correct type might as well be used.
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: 67814c00de3161181cddd06c77aeaf86ac4cc584 , < 1344b632cb5043e32939a84568125719111c5af3 (git)
Affected: 67814c00de3161181cddd06c77aeaf86ac4cc584 , < 2a5cfcad1d56e26d645b7887b0ed24c371851525 (git)
Affected: 67814c00de3161181cddd06c77aeaf86ac4cc584 , < 5bd63cad9df4328a184c409fbdad4f17944bcdb8 (git)
Affected: 67814c00de3161181cddd06c77aeaf86ac4cc584 , < 3e8ec7c0387273329374f5c7bd61f5f38af71fe1 (git)
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Linux Linux Affected: 6.8
Unaffected: 0 , < 6.8 (semver)
Unaffected: 6.12.104 , ≤ 6.12.* (semver)
Unaffected: 6.18.45 , ≤ 6.18.* (semver)
Unaffected: 7.1.9 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
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          "product": "Linux",
          "programFiles": [
            "fs/verity/measure.c"
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              "operator": "OR"
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      "descriptions": [
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nfsverity: Fix bpf_get_fsverity_digest() dynptr assumptions\n\nThe BPF verifier and the dynptr abstraction ensure that the memory space\nreferenced by a dynptr remains valid.  They do not, however, provide any\nguarantee that the contents of the memory are stable.  kfuncs are\nexpected to remain memory-safe even if concurrent modifications occur.\n\nbpf_get_fsverity_digest() didn\u0027t follow that: it could crash if\narg-\u003edigest_size was concurrently modified.\n\nFix that by using the known-good value hash_alg-\u003edigest_size instead.\n\nAlso widen \u0027dynptr_sz\u0027 and \u0027out_digest_sz\u0027 to u64 to match the return\ntype of __bpf_dynptr_size().  It doesn\u0027t appear that it can actually be\nmore than INT_MAX currently (since __bpf_dynptr_data_rw() excludes\nfile-based pointers), but the correct type might as well be used."
        }
      ],
      "metrics": [
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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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              "value": "AV:L - The bug is only reachable via bpf_get_fsverity_digest(), a BPF kfunc callable from BPF LSM programs loaded through the bpf(2) syscall and triggered by local LSM hooks such as file_open, not by any network-facing kernel service.\nAC:L - Exploitation requires racing concurrent writes to the dynptr-backed fsverity_digest buffer (e.g., bpf_map_update_elem from a sibling thread) against the kfunc\u0027s memset; the attacker controls both sides of this race and can repeat it until the bad offset is hit.\nPR:L - Loading and attaching the required BPF LSM program needs CAP_BPF and CAP_PERFMON, which an unprivileged user can obtain as root inside a user namespace (unshare -Ur) without init-namespace privileges, matching kernel CNA guidance for BPF reachability.\nUI:N - No victim interaction is required; the attacker can load the LSM program, prepare a shared dynptr buffer, enable fsverity on a file they own, and trigger file_open themselves to invoke the vulnerable kfunc.\nS:U - Successful exploitation corrupts kernel heap memory and can yield local privilege escalation within the same kernel/host security boundary; it does not by itself cross a guest-to-host, sandbox, or IOMMU isolation boundary.\nC:H - Concurrent tampering with digest_size lets memset() use an attacker-chosen offset beyond the dynptr allocation, causing out-of-bounds kernel heap writes that can corrupt adjacent objects and be leveraged for arbitrary kernel memory disclosure.\nI:H - The faulty memset() can write large zeroed regions far outside the dynptr buffer, giving a controllable out-of-bounds heap write primitive that is exploitable for control-flow hijacking and arbitrary kernel code execution.\nA:H - An out-of-bounds heap write from kernel context can immediately oops/panic the kernel or destabilize critical structures, and the underlying memory corruption reliably threatens system availability even before full exploitation."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-25T05:40:17.568Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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        },
        {
          "url": "https://git.kernel.org/stable/c/3e8ec7c0387273329374f5c7bd61f5f38af71fe1"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74590",
    "datePublished": "2026-08-22T15:31:41.929Z",
    "dateReserved": "2026-08-15T05:44:03.918Z",
    "dateUpdated": "2026-08-25T05:40:17.568Z",
    "state": "PUBLISHED"
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-25T08:49:39+00:00",
      "cve": "CVE-2026-74590",
      "id": "CVE-2026-74590",
      "initial_release_date": "2026-08-22T00:00:00+00:00",
      "product_status:known_affected": "184",
      "product_status:known_not_affected": "90",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: fsverity: Fix bpf_get_fsverity_digest() dynptr assumptions",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-74590.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.

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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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  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
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  • 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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