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CVE Record

CVE-2021-47323: watchdog: sc520_wdt: Fix possible use-after-free in wdt_turnoff()

In the Linux kernel, the following vulnerability has been resolved: watchdog: sc520_wdt: Fix possible use-after-free in wdt_turnoff() This module's remove path calls del_timer(). However, that function does not wait until the timer handler finishes. This means that the timer handler may still be running after the driver's remove function has finished, which would result in a use-after-free. Fix by calling del_timer_sync(), which makes sure the timer handler has finished, and unable to re-schedule itself.

HighCVSS 8.8Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2021-47323 is a Linux kernel use-after-free in the sc520_wdt watchdog driver. During driver removal, a timer handler could continue running after the driver cleanup completed. That can corrupt memory and potentially affect confidentiality, integrity, and availability on systems carrying the vulnerable code.

Executive priority

Treat as a high-priority kernel maintenance issue, not as confirmed active exploitation. Focus on identifying exposed Linux systems, confirming vendor patch status, and scheduling kernel updates where the vulnerable watchdog driver could exist.

Technical view

The vulnerable remove path uses del_timer(), which does not wait for an active timer callback to finish. If the sc520_wdt timer handler continues after teardown, freed driver state may be accessed. The kernel fix replaces this with del_timer_sync(), preventing the handler from running or rescheduling after removal.

Likely exposure

Exposure is most relevant to Linux systems on affected kernel branches that include the sc520_wdt watchdog driver. The CVE lists affected versions through 5.14 and provides stable kernel fix commits. Distribution kernels may have backported fixes, so version strings alone are not conclusive.

Exploitation context

The source bundle does not show CISA KEV listing or other evidence of active exploitation. The CVSS vector is high impact and low complexity with low privileges required, but the provided sources do not describe real-world exploitation or trigger details beyond the timer-removal flaw.

Researcher notes

Evidence is limited to the CVE description and upstream stable commits. The core condition is a race between driver removal and a watchdog timer callback. Validate exposure carefully because distro kernels may carry the fix without matching upstream version numbers.

Mitigation direction

  • Update to a kernel containing the relevant stable fix commit for your branch.
  • Check distribution security advisories for backported fixes before relying on upstream version numbers.
  • Prioritize systems where the sc520_wdt watchdog driver is present or enabled.
  • Avoid unsupported kernel branches where vendor fixes are unavailable.
  • Follow vendor guidance for any temporary driver or module policy changes.

Validation and detection

  • Inventory Linux kernel versions and map them to vendor advisory status.
  • Confirm whether the sc520_wdt watchdog driver is built, loaded, or packaged.
  • Verify the applicable del_timer_sync() fix is present in the vendor kernel source.
  • Check vulnerability scanner findings against distribution backport metadata.
  • Document systems requiring maintenance windows for kernel replacement or reboot.
Prepared
Confidence
high
Sources
11

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

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-416: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-47323 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
8.8 (3.1)
Known Exploited
No
Published

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

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.

1CVSS vectors
3Timeline events
2ADP providers
10Source links

SSVC decision data

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

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
8.8CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H2.85.9CISA-ADP

Vulnerability scoring details

Base CVSS 3.1 score

8.8High
CVSS 3.1 vector shape for CVE-2021-47323Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

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

CISA-ADPCISA ADP Vulnrichment
cvssV3_1other:ssvc
CVECVE Program Container

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
LinuxLinux1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2unaffected
LinuxLinux2.6.12, 0, 4.4.276, 4.9.276, 4.14.240, 4.19.198, 5.4.134, 5.10.52, 5.12.19, 5.13.4, 5.14affected
Weakness

CWE details

CWE-416

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

CWE-416 · source CWE mapping

Use After Free

Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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