CVE-2021-47393

What it is

In the Linux kernel, the following vulnerability has been resolved: hwmon: (mlxreg-fan) Return non-zero value when fan current state is enforced from sysfs Fan speed minimum can be enforced from sysfs. For example, setting current fan speed to 20 is used to enforce fan speed to be at 100% speed, 19 - to be not below 90% speed, etcetera. This feature provides ability to limit fan speed according to some system wise considerations, like absence of some replaceable units or high system ambient temperature. Request for changing fan minimum speed is configuration request and can be set only through 'sysfs' write procedure. In this situation value of argument 'state' is above nominal fan speed maximum. Return non-zero code in this case to avoid thermal_cooling_device_stats_update() call, because in this case statistics update violates thermal statistics table range. The issues is observed in case kernel is configured with option CONFIG_THERMAL_STATISTICS. Here is the trace from KASAN: [ 159.506659] BUG: KASAN: slab-out-of-bounds in thermal_cooling_device_stats_update+0x7d/0xb0 [ 159.516016] Read of size 4 at addr ffff888116163840 by task hw-management.s/7444 [ 159.545625] Call Trace: [ 159.548366] dump_stack+0x92/0xc1 [ 159.552084] ? thermal_cooling_device_stats_update+0x7d/0xb0 [ 159.635869] thermal_zone_device_update+0x345/0x780 [ 159.688711] thermal_zone_device_set_mode+0x7d/0xc0 [ 159.694174] mlxsw_thermal_modules_init+0x48f/0x590 [mlxsw_core] [ 159.700972] ? mlxsw_thermal_set_cur_state+0x5a0/0x5a0 [mlxsw_core] [ 159.731827] mlxsw_thermal_init+0x763/0x880 [mlxsw_core] [ 160.070233] RIP: 0033:0x7fd995909970 [ 160.074239] Code: 73 01 c3 48 8b 0d 28 d5 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 99 2d 2c 00 00 75 10 b8 01 00 00 00 0f 05 <48> 3d 01 f0 ff .. [ 160.095242] RSP: 002b:00007fff54f5d938 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 [ 160.103722] RAX: ffffffffffffffda RBX: 0000000000000013 RCX: 00007fd995909970 [ 160.111710] RDX: 0000000000000013 RSI: 0000000001906008 RDI: 0000000000000001 [ 160.119699] RBP: 0000000001906008 R08: 00007fd995bc9760 R09: 00007fd996210700 [ 160.127687] R10: 0000000000000073 R11: 0000000000000246 R12: 0000000000000013 [ 160.135673] R13: 0000000000000001 R14: 00007fd995bc8600 R15: 0000000000000013 [ 160.143671] [ 160.145338] Allocated by task 2924: [ 160.149242] kasan_save_stack+0x19/0x40 [ 160.153541] __kasan_kmalloc+0x7f/0xa0 [ 160.157743] __kmalloc+0x1a2/0x2b0 [ 160.161552] thermal_cooling_device_setup_sysfs+0xf9/0x1a0 [ 160.167687] __thermal_cooling_device_register+0x1b5/0x500 [ 160.173833] devm_thermal_of_cooling_device_register+0x60/0xa0 [ 160.180356] mlxreg_fan_probe+0x474/0x5e0 [mlxreg_fan] [ 160.248140] [ 160.249807] The buggy address belongs to the object at ffff888116163400 [ 160.249807] which belongs to the cache kmalloc-1k of size 1024 [ 160.263814] The buggy address is located 64 bytes to the right of [ 160.263814] 1024-byte region [ffff888116163400, ffff888116163800) [ 160.277536] The buggy address belongs to the page: [ 160.282898] page:0000000012275840 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888116167000 pfn:0x116160 [ 160.294872] head:0000000012275840 order:3 compound_mapcount:0 compound_pincount:0 [ 160.303251] flags: 0x200000000010200(slab|head|node=0|zone=2) [ 160.309694] raw: 0200000000010200 ffffea00046f7208 ffffea0004928208 ffff88810004dbc0 [ 160.318367] raw: ffff888116167000 00000000000a0006 00000001ffffffff 0000000000000000 [ 160.327033] page dumped because: kasan: bad access detected [ 160.333270] [ 160.334937] Memory state around the buggy address: [ 160.356469] >ffff888116163800: fc ..

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of data exposure, service disruption.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2024-05-21 15:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 04:17 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 7.1 HIGH (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2024-05-21 15:15 UTC

Last modified

2026-06-17 04:17 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-125 · Out-of-bounds read

Record status

Analyzed

Affected

• Linux Kernel < 4.19.209
• Linux Kernel < 5.4.151
• Linux Kernel < 5.10.71
• Linux Kernel < 5.14.10
• Linux Kernel 5.15

Attack profile CVSS 3.1 · 7.1

Attack vector

Local

Complexity

Low

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

High

Is it in your code?

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