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NVD / CVE Program· CNA Linux

CVE-2021-47327: iommu/arm-smmu: Fix arm_smmu_device refcount leak when arm_smmu_rpm_get fails

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 1adf30f198c26539a62d761e45af72cde570413d, 3761ae0d0e549f2acdaf11f49df4ed06d256b20f, c4007596fbdabc29f858dc2e1990858a146b60b2.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 1adf30f198c26539a62d761e45af72cde570413d, 3761ae0d0e549f2acdaf11f49df4ed06d256b20f, c4007596fbdabc29f858dc2e1990858a146b60b2 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: iommu/arm-smmu: Fix arm_smmu_device refcount leak when arm_smmu_rpm_get fails arm_smmu_rpm_get() invokes pm_runtime_get_sync(), which increases the refcount of the "smmu" even though the return value is less than 0. The reference counting issue happens in some error handling paths of arm_smmu_rpm_get() in its caller functions. When arm_smmu_rpm_get() fails, the caller functions forget to decrease the refcount of "smmu" increased by arm_smmu_rpm_get(), causing a refcount leak. Fix this issue by calling pm_runtime_resume_and_get() instead of pm_runtime_get_sync() in arm_smmu_rpm_get(), which can keep the refcount balanced in case of failure.

HighCVSS 7.1 · v3.1—No exploit Fix available
Published
May 21, 2024
Updated
Jun 17, 2026
EPSS
0.2% · 17th 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-2021-47327

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

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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.

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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 kernelbefore 5.4.134
  • linux linux kernel5.5 and later · before 5.10.52
  • linux linux kernel5.11 and later · before 5.12.19
  • linux linux kernel5.13 and later · before 5.13.4

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

    • 5.0affected
    • d4a44f0750bb9bf7c44c22444a482756b2344a79 and later · before 3761ae0d0e549f2acdaf11f49df4ed06d256b20faffected · git
    • d4a44f0750bb9bf7c44c22444a482756b2344a79 and later · before c4007596fbdabc29f858dc2e1990858a146b60b2affected · git
    • d4a44f0750bb9bf7c44c22444a482756b2344a79 and later · before fbf4daa6f4105e01fbd3868006f65c163365c1e3affected · git
    • d4a44f0750bb9bf7c44c22444a482756b2344a79 and later · before fe92c058199067ae90cf2a901ddf3c271893557aaffected · git
    • d4a44f0750bb9bf7c44c22444a482756b2344a79 and later · before 1adf30f198c26539a62d761e45af72cde570413daffected · git
    • before 5.0not affected · semver
    • 5.4.134 and later · up to and including 5.4.*not affected · semver
    • 5.10.52 and later · up to and including 5.10.*not affected · semver
    • 5.12.19 and later · up to and including 5.12.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 5.14.6-15.14.6-1

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-2021-47324May 21, 2024 · watchdog: Fix possible use-after-free in wdt_startup()
    35Monitor
  • ← EarlierCVE-2021-47325May 21, 2024 · iommu/arm-smmu: Fix arm_smmu_device refcount leak in address translation
    22Monitor
  • Later →CVE-2021-47328May 21, 2024 · scsi: iscsi: Fix conn use after free during resets
    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 Linux1adf30f198c26539a62d761e45af72cde570413dVendor (CNA)
Linux Linux3761ae0d0e549f2acdaf11f49df4ed06d256b20fVendor (CNA)
Linux Linuxc4007596fbdabc29f858dc2e1990858a146b60b2Vendor (CNA)
Linux Linuxfbf4daa6f4105e01fbd3868006f65c163365c1e3Vendor (CNA)
Linux Linuxfe92c058199067ae90cf2a901ddf3c271893557aVendor (CNA)
debian:linux5.14.6-1 · Debian:12Package registry (OSV)

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.

  • CVE-2023-5633211 days apartKernel: vmwgfx: reference count issue leads to use-after-free in surface handling
    31Monitor
  • CVE-2023-2019393 days apartA flaw was found in the Linux kernel's netdevsim device driver, within the scheduling of events.
    17Monitor

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-911 · Improper Update of Reference Count

CVSS vector

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

nvd-secondary

Attack context

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

MITRE has no CAPEC/ATT&CK mapping for this CWE.

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