HighFix available

efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare Observed on kernel 6.6 (present on master as well): BUG: KASAN: slab-out-of-bounds in memcmp+0x98/0xd0 Call trace: kasan_check_range+0xe8/0x190 __asan_loadN+0x1c/0x28 memcmp+0x98/0xd0 efivarfs_d_compare+0x68/0xd8 __d_lookup_rcu_op_compare+0x178/0x218 __d_lookup_rcu+0x1f8/0x228 d_alloc_parallel+0x150/0x648 lookup_open.isra.0+0x5f0/0x8d0 open_last_lookups+0x264/0x828 path_openat+0x130/0x3f8 do_filp_open+0x114/0x248 do_sys_openat2+0x340/0x3c0 __arm64_sys_openat+0x120/0x1a0 If dentry->d_name.len < EFI_VARIABLE_GUID_LEN , 'guid' can become negative, leadings to oob. The issue can be triggered by parallel lookups using invalid filename: T1 T2 lookup_open ->lookup simple_lookup d_add // invalid dentry is added to hash list lookup_open d_alloc_parallel __d_lookup_rcu __d_lookup_rcu_op_compare hlist_bl_for_each_entry_rcu // invalid dentry can be retrieved ->d_compare efivarfs_d_compare // oob Fix it by checking 'guid' before cmp.

Products: Kernel
Affected versions: Not specified
Fixed versions: 5.10.242, 5.15.191, 5.4.298, 6.1.150, 6.12.45, 6.16.5, 6.6.104
CVEs: CVE-2025-39817
Confirmed fixed CVEs: Not specified
Updated in this feed: 3 Nov 2026, 15:34 UTC · Revision 1

Source evidence

efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare

core-osv · Original source

Published 16 Sept 2025, 13:00 UTC

osv:CVE-2025-39817

Kernel

Fixed versions: 5.4.298, 5.10.242, 5.15.191, 6.1.150, 6.6.104, 6.12.45, 6.16.5

Complete source record

{
  "id": "7364eca6364199b06c251b41da104906c117202434537f43ece265543f860080",
  "url": "https://osv.dev/vulnerability/CVE-2025-39817",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare Observed on kernel 6.6 (present on master as well): BUG: KASAN: slab-out-of-bounds in memcmp+0x98/0xd0 Call trace: kasan_check_range+0xe8/0x190 __asan_loadN+0x1c/0x28 memcmp+0x98/0xd0 efivarfs_d_compare+0x68/0xd8 __d_lookup_rcu_op_compare+0x178/0x218 __d_lookup_rcu+0x1f8/0x228 d_alloc_parallel+0x150/0x648 lookup_open.isra.0+0x5f0/0x8d0 open_last_lookups+0x264/0x828 path_openat+0x130/0x3f8 do_filp_open+0x114/0x248 do_sys_openat2+0x340/0x3c0 __arm64_sys_openat+0x120/0x1a0 If dentry->d_name.len < EFI_VARIABLE_GUID_LEN , 'guid' can become negative, leadings to oob. The issue can be triggered by parallel lookups using invalid filename: T1 T2 lookup_open ->lookup simple_lookup d_add // invalid dentry is added to hash list lookup_open d_alloc_parallel __d_lookup_rcu __d_lookup_rcu_op_compare hlist_bl_for_each_entry_rcu // invalid dentry can be retrieved ->d_compare efivarfs_d_compare // oob Fix it by checking 'guid' before cmp.",
    "evidence": "osv:CVE-2025-39817",
    "products": [
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        "fixed_versions": [
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    "severity": "high",
    "structured": {
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      "aliases": [
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      "metrics": [
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          "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H"
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      "modified": "2026-10-28T02:30:29.933922630Z",
      "provider": "osv",
      "references": [
        "https://cert-portal.siemens.com/productcert/html/ssa-032379.html",
        "https://git.kernel.org/stable/c/0f63fbabeaaaaaaf5b742a2f4c1b4590d50bf1f6",
        "https://git.kernel.org/stable/c/568e7761279b99c6daa3002290fd6d8047ddb6d2",
        "https://git.kernel.org/stable/c/71581a82f38e5a4d807d71fc1bb59aead80ccf95",
        "https://git.kernel.org/stable/c/794399019301944fd6d2e0d7a51b3327e26c410e",
        "https://git.kernel.org/stable/c/925599eba46045930b850a98ae594d2e3028ac40",
        "https://git.kernel.org/stable/c/a6358f8cf64850f3f27857b8ed8c1b08cfc4685c",
        "https://git.kernel.org/stable/c/c2925cd6207079c3f4d040d082515db78d63afbf",
        "https://git.kernel.org/stable/c/d7f5e35e70507d10cbaff5f9e194ed54c4ee14f7",
        "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html",
        "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39817.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-39817",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/39xxx/CVE-2025-39817.json"
      }
    },
    "related_cves": [
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        "evidence": "/id"
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    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 496856,
  "published_at": "2025-09-16T13:00:17.776+00:00"
}