GHSA-M685-84XG-FVFJ
Vulnerability from github – Published: 2025-09-16 15:32 – Updated: 2026-05-12 15:31In 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.
{
"affected": [],
"aliases": [
"CVE-2025-39817"
],
"database_specific": {
"cwe_ids": [
"CWE-125"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-09-16T13:15:57Z",
"severity": "HIGH"
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nefivarfs: Fix slab-out-of-bounds in efivarfs_d_compare\n\nObserved on kernel 6.6 (present on master as well):\n\n BUG: KASAN: slab-out-of-bounds in memcmp+0x98/0xd0\n Call trace:\n kasan_check_range+0xe8/0x190\n __asan_loadN+0x1c/0x28\n memcmp+0x98/0xd0\n efivarfs_d_compare+0x68/0xd8\n __d_lookup_rcu_op_compare+0x178/0x218\n __d_lookup_rcu+0x1f8/0x228\n d_alloc_parallel+0x150/0x648\n lookup_open.isra.0+0x5f0/0x8d0\n open_last_lookups+0x264/0x828\n path_openat+0x130/0x3f8\n do_filp_open+0x114/0x248\n do_sys_openat2+0x340/0x3c0\n __arm64_sys_openat+0x120/0x1a0\n\nIf dentry-\u003ed_name.len \u003c EFI_VARIABLE_GUID_LEN , \u0027guid\u0027 can become\nnegative, leadings to oob. The issue can be triggered by parallel\nlookups using invalid filename:\n\n T1\t\t\tT2\n lookup_open\n -\u003elookup\n simple_lookup\n d_add\n // invalid dentry is added to hash list\n\n\t\t\tlookup_open\n\t\t\t d_alloc_parallel\n\t\t\t __d_lookup_rcu\n\t\t\t __d_lookup_rcu_op_compare\n\t\t\t hlist_bl_for_each_entry_rcu\n\t\t\t // invalid dentry can be retrieved\n\t\t\t -\u003ed_compare\n\t\t\t efivarfs_d_compare\n\t\t\t // oob\n\nFix it by checking \u0027guid\u0027 before cmp.",
"id": "GHSA-m685-84xg-fvfj",
"modified": "2026-05-12T15:31:08Z",
"published": "2025-09-16T15:32:35Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-39817"
},
{
"type": "WEB",
"url": "https://cert-portal.siemens.com/productcert/html/ssa-032379.html"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0f63fbabeaaaaaaf5b742a2f4c1b4590d50bf1f6"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/568e7761279b99c6daa3002290fd6d8047ddb6d2"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/71581a82f38e5a4d807d71fc1bb59aead80ccf95"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/794399019301944fd6d2e0d7a51b3327e26c410e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/925599eba46045930b850a98ae594d2e3028ac40"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/a6358f8cf64850f3f27857b8ed8c1b08cfc4685c"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/c2925cd6207079c3f4d040d082515db78d63afbf"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d7f5e35e70507d10cbaff5f9e194ed54c4ee14f7"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html"
},
{
"type": "WEB",
"url": "https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H",
"type": "CVSS_V3"
}
]
}
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