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CVE Record

CVE-2021-47202: thermal: Fix NULL pointer dereferences in of_thermal_ functions

In the Linux kernel, the following vulnerability has been resolved: thermal: Fix NULL pointer dereferences in of_thermal_ functions of_parse_thermal_zones() parses the thermal-zones node and registers a thermal_zone device for each subnode. However, if a thermal zone is consuming a thermal sensor and that thermal sensor device hasn't probed yet, an attempt to set trip_point_*_temp for that thermal zone device can cause a NULL pointer dereference. Fix it. console:/sys/class/thermal/thermal_zone87 # echo 120000 > trip_point_0_temp ... Unable to handle kernel NULL pointer dereference at virtual address 0000000000000020 ... Call trace: of_thermal_set_trip_temp+0x40/0xc4 trip_point_temp_store+0xc0/0x1dc dev_attr_store+0x38/0x88 sysfs_kf_write+0x64/0xc0 kernfs_fop_write_iter+0x108/0x1d0 vfs_write+0x2f4/0x368 ksys_write+0x7c/0xec __arm64_sys_write+0x20/0x30 el0_svc_common.llvm.7279915941325364641+0xbc/0x1bc do_el0_svc+0x28/0xa0 el0_svc+0x14/0x24 el0_sync_handler+0x88/0xec el0_sync+0x1c0/0x200 While at it, fix the possible NULL pointer dereference in other functions as well: of_thermal_get_temp(), of_thermal_set_emul_temp(), of_thermal_get_trend().

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysisunknown

Security readout for executives and security teams

Plain-English summary

This Linux kernel issue can crash affected systems when thermal management code handles a thermal zone before its sensor device is ready. The public record describes a NULL pointer dereference, which is primarily an availability risk. No active exploitation is cited, and severity scoring is not provided.

Executive priority

Treat as a targeted availability concern, especially for embedded, appliance, and ARM-based Linux estates. Prioritize normal kernel maintenance unless critical devices match the affected thermal configuration or show related crashes.

Technical view

The flaw is in Linux thermal device-tree helpers. of_parse_thermal_zones() may register zones whose sensor has not probed, and later thermal operations can dereference NULL in of_thermal_set_trip_temp(), get_temp(), set_emul_temp(), or get_trend(). Stable kernel fixes are referenced.

Likely exposure

Exposure is most likely on Linux systems using device-tree based thermal zones and affected kernel branches or vendor kernels missing the referenced stable fixes. Distribution backports may change version-only conclusions, so validate against vendor kernel packages.

Exploitation context

The source shows a local sysfs write path triggering a kernel NULL pointer dereference. KEV status is false, and the provided sources do not cite public exploitation, remote exploitation, privilege escalation, or data compromise.

Researcher notes

Evidence supports a kernel NULL dereference in thermal framework helpers, fixed by stable commits. The bundle lacks CVSS, CWE, detailed affected CPEs, and exploitation evidence, so exposure analysis depends on kernel provenance and vendor backports.

Mitigation direction

  • Check Linux distribution or device vendor guidance for this CVE.
  • Update to a kernel package containing the referenced stable fixes.
  • For embedded devices, confirm board vendor kernel trees include the thermal fixes.
  • Restrict thermal sysfs write access to trusted administrative paths.
  • Monitor vendor advisories for affected backported kernel builds.

Validation and detection

  • Inventory Linux kernel versions across servers, appliances, and embedded devices.
  • Identify systems using device-tree thermal zones or vendor board kernels.
  • Confirm kernel source or package changelogs include the referenced fix commits.
  • Review crash logs for NULL pointer dereferences in of_thermal_* functions.
  • Verify vendor kernels are not relying on version numbers alone.
Prepared
Confidence
medium
Sources
7

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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ATT&CK lookup starting points

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CVE-2021-47202 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
3Timeline events
2ADP providers
6Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. CVE publishedCVE Program

    The CVE record was published.

  3. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CVECVE Program Container
CISA-ADPCISA ADP Vulnrichment
other:ssvc

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux2251aef64a38db60f4ae7a4a83f9203c6791f196, 2251aef64a38db60f4ae7a4a83f9203c6791f196, 2251aef64a38db60f4ae7a4a83f9203c6791f196, 2251aef64a38db60f4ae7a4a83f9203c6791f196, 2251aef64a38db60f4ae7a4a83f9203c6791f196unaffected
LinuxLinux3.19, 0, 5.4.210, 5.10.81, 5.14.21, 5.15.4, 5.16affected
Weakness

CWE details

No CWE listed

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.