{"cve":"CVE-2025-39817","nvd":{"published":"2025-09-16T13:15:57.187","modified":"2026-10-19T21:10:00.160","status":"Modified","description":"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->d_name.len < EFI_VARIABLE_GUID_LEN , 'guid' 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   ->lookup\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     ->d_compare\n\t\t\t      efivarfs_d_compare\n\t\t\t      // oob\n\nFix it by checking 'guid' before cmp.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H","score":7.1},"cwes":["CWE-125"],"references":["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"],"products":["debian:debian_linux","linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-21T03:43:09.190223697+00:00"},"epss":{"cve":"CVE-2025-39817","score":0.00167,"percentile":0.05916,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}