Answer in brief
CVE-2025-39817 records a Unknown severity vulnerability in efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC CN 4100 (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2025-39817 records a Unknown severity vulnerability in efivarfs: Fix slab-out-of-bounds in efivarfs_d_compare. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC CN 4100 (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC CN 4100 (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <0f63fbabeaaaaaaf5b742a2f4c1b4590d50bf1f6 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <794399019301944fd6d2e0d7a51b3327e26c410e || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <568e7761279b99c6daa3002290fd6d8047ddb6d2 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <d7f5e35e70507d10cbaff5f9e194ed54c4ee14f7 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <925599eba46045930b850a98ae594d2e3028ac40 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <c2925cd6207079c3f4d040d082515db78d63afbf || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <71581a82f38e5a4d807d71fc1bb59aead80ccf95 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <a6358f8cf64850f3f27857b8ed8c1b08cfc4685c || 688289c4b745c018b3449b4b4c5a2030083c8eaf || >=3.8.2 <3.9 | 0f63fbabeaaaaaaf5b742a2f4c1b4590d50bf1f6, 794399019301944fd6d2e0d7a51b3327e26c410e, 568e7761279b99c6daa3002290fd6d8047ddb6d2, d7f5e35e70507d10cbaff5f9e194ed54c4ee14f7, 925599eba46045930b850a98ae594d2e3028ac40, c2925cd6207079c3f4d040d082515db78d63afbf, 71581a82f38e5a4d807d71fc1bb59aead80ccf95, a6358f8cf64850f3f27857b8ed8c1b08cfc4685c, 3.9 |
| Linux/Linuxgeneric | 3.9 | Not reported |
| Siemens/SIMATIC CN 4100generic | >=0 <V5.0 | V5.0 |
Published upstream
Sep 16, 2025
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.
Quoted source text, attributed separately from HOL analysis.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Linux/Linux (generic), Linux/Linux (generic), Siemens/SIMATIC CN 4100 (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Linux/Linuxgeneric | >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <0f63fbabeaaaaaaf5b742a2f4c1b4590d50bf1f6 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <794399019301944fd6d2e0d7a51b3327e26c410e || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <568e7761279b99c6daa3002290fd6d8047ddb6d2 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <d7f5e35e70507d10cbaff5f9e194ed54c4ee14f7 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <925599eba46045930b850a98ae594d2e3028ac40 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <c2925cd6207079c3f4d040d082515db78d63afbf || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <71581a82f38e5a4d807d71fc1bb59aead80ccf95 || >=da27a24383b2b10bf6ebd0db29b325548aafecb4 <a6358f8cf64850f3f27857b8ed8c1b08cfc4685c || 688289c4b745c018b3449b4b4c5a2030083c8eaf || >=3.8.2 <3.9 | 0f63fbabeaaaaaaf5b742a2f4c1b4590d50bf1f6, 794399019301944fd6d2e0d7a51b3327e26c410e, 568e7761279b99c6daa3002290fd6d8047ddb6d2, d7f5e35e70507d10cbaff5f9e194ed54c4ee14f7, 925599eba46045930b850a98ae594d2e3028ac40, c2925cd6207079c3f4d040d082515db78d63afbf, 71581a82f38e5a4d807d71fc1bb59aead80ccf95, a6358f8cf64850f3f27857b8ed8c1b08cfc4685c, 3.9 |
| Linux/Linuxgeneric | 3.9 | Not reported |
| Siemens/SIMATIC CN 4100generic | >=0 <V5.0 | V5.0 |
Published upstream
Sep 16, 2025
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 5, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 5, 2026
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.
Quoted source text, attributed separately from HOL analysis.