Skip to content
Noroxi
NVD / CVE Program· CNA Linux

CVE-2021-47393: hwmon: (mlxreg-fan) Return non-zero value when fan current state is enforced from sysfs

Noroxi assessment

Priority: Monitor (action score 28/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.25% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: Linux Linux 5c6e0bce647d9cb32a17d58ffa669b3421fcc6ca, 76bbb482d33bfcd7e9070ecf594c9ec73e01c930, a6c42ae1530f94724d3c42cf91fe3d3c5e394f8a.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 5c6e0bce647d9cb32a17d58ffa669b3421fcc6ca, 76bbb482d33bfcd7e9070ecf594c9ec73e01c930, a6c42ae1530f94724d3c42cf91fe3d3c5e394f8a or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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 ..

HighCVSS 7.1 · v3.1—No exploit Fix available
Published
May 21, 2024
Updated
Jun 17, 2026
EPSS
0.2% · 16th percentile

Report tools

JSON

Action score

28

Monitor

Low priority for now.

CVSS
28 / 40 · 7.1 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-47393

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for linux records
Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel4.19 and later · before 4.19.209
  • linux linux kernel4.20 and later · before 5.4.151
  • linux linux kernel5.5 and later · before 5.10.71
  • linux linux kernel5.11 and later · before 5.14.10
  • linux linux kernel5.15

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 4.19affected
    • 65afb4c8e7e4e7e74b28efa1df62da503ca3e7a6 and later · before 5c6e0bce647d9cb32a17d58ffa669b3421fcc6caaffected · git
    • 65afb4c8e7e4e7e74b28efa1df62da503ca3e7a6 and later · before a6c42ae1530f94724d3c42cf91fe3d3c5e394f8aaffected · git
    • 65afb4c8e7e4e7e74b28efa1df62da503ca3e7a6 and later · before 76bbb482d33bfcd7e9070ecf594c9ec73e01c930affected · git
    • 65afb4c8e7e4e7e74b28efa1df62da503ca3e7a6 and later · before aa85fb7bde558bb2e364e85976b14b259c8b6fe8affected · git
    • 65afb4c8e7e4e7e74b28efa1df62da503ca3e7a6 and later · before e6fab7af6ba1bc77c78713a83876f60ca7a4a064affected · git
    • before 4.19not affected · semver
    • 4.19.209 and later · up to and including 4.19.*not affected · semver
    • 5.4.151 and later · up to and including 5.4.*not affected · semver
    • 5.10.71 and later · up to and including 5.10.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernelbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-corebefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-cross-headersbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debugbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-corebefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-develbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-develbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-docbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-headersbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-modulesbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-modules-extrabefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-rtbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-corebefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debugbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-kvmbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-develbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10

+96

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
    90Now
  • CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe…KEV
    89Now
  • CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
    85Now

Published before and after this one in the same product

  • ← EarlierCVE-2021-47391May 21, 2024 · RDMA/cma: Ensure rdma_addr_cancel() happens before issuing more requests
    31Monitor
  • ← EarlierCVE-2021-47392May 21, 2024 · RDMA/cma: Fix listener leak in rdma_cma_listen_on_all() failure
    22Monitor
  • Later →CVE-2021-47394May 21, 2024 · netfilter: nf_tables: unlink table before deleting it
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux5c6e0bce647d9cb32a17d58ffa669b3421fcc6caVendor (CNA)
Linux Linux76bbb482d33bfcd7e9070ecf594c9ec73e01c930Vendor (CNA)
Linux Linuxa6c42ae1530f94724d3c42cf91fe3d3c5e394f8aVendor (CNA)
Linux Linuxaa85fb7bde558bb2e364e85976b14b259c8b6fe8Vendor (CNA)
Linux Linuxe6fab7af6ba1bc77c78713a83876f60ca7a4a064Vendor (CNA)
almalinux:bpftool4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-abi-stablelists4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-core4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-cross-headers4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-core4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-devel4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules-extra4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-devel4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-doc4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
debian:linux5.14.12-1 · Debian:12Package registry (OSV)
red hat:bpftool-debuginfo0:7.0.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-debuginfo0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debug-devel-matched0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-debuginfo0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-64k-devel-matched0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-debuginfo0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debug-devel-matched0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debuginfo0:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)
red hat:kernel-debuginfo-common-aarch640:5.14.0-284.11.1.el9_2 · Red Hat:enterprise_linux:9::appstreamPackage registry (OSV)

+2

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records