CVE-2025-39817
Unknown Unknown - Not Provided
BaseFortify

Publication date: 2025-09-16

Last updated on: 2025-11-03

Assigner: kernel.org

Description
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.
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Meta Information
Published
2025-09-16
Last Modified
2025-11-03
Generated
2026-05-07
AI Q&A
2025-09-16
EPSS Evaluated
2026-05-05
NVD
CVE-2025-39817
Affected Vendors & Products
Showing 3 associated CPEs
Vendor Product Version / Range
linux linux_kernel 5.10.244
linux linux_kernel 6.6
linux linux_kernel 6.1.153
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?

This vulnerability is a slab-out-of-bounds memory access in the Linux kernel's efivarfs component, specifically in the efivarfs_d_compare function. It occurs when the length of a dentry name is less than the expected EFI variable GUID length, causing a 'guid' value to become negative and leading to out-of-bounds memory access. This can be triggered by parallel lookups using invalid filenames, which add invalid dentries to the hash list and cause the vulnerable function to access memory incorrectly. The issue was fixed by adding a check on the 'guid' value before comparison.


How can this vulnerability impact me? :

This vulnerability can lead to out-of-bounds memory access in the Linux kernel, which may cause system instability, crashes, or potentially allow an attacker to execute arbitrary code or escalate privileges by exploiting the memory corruption.


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