CVE-2021-47327

Kernel resource exhaustion via SMMU refcount leak

Published May 21, 2024 · Updated May 11, 2026

Reference-count leakage in affected Linux kernel releases allows local users to interrupt service through kernel resource exhaustion. The arm_smmu_rpm_get function calls pm_runtime_get_sync, which increments the SMMU runtime reference count even when resume fails, while caller error paths omit the matching decrement. Exploitation requires local low-privileged access, an ARM SMMU configuration, and a runtime power-management failure; public sources do not explain CISA's assessed confidentiality impact.

CVSS severity7.1
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reference-count leakage in affected Linux kernel releases allows local users to interrupt service through kernel resource exhaustion. The arm_smmu_rpm_get function calls pm_runtime_get_sync, which increments the SMMU runtime reference count even when resume fails, while caller error paths omit the matching decrement. Exploitation requires local low-privileged access, an ARM SMMU configuration, and a runtime power-management failure; public sources do not explain CISA's assessed confidentiality impact.

The record

CVE
CVE-2021-47327
Published
May 21, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-911, T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. May 11, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.0
  2. Affected versionversion=d4a44f0750bb9bf7c44c22444a482756b2344a79 <1adf30f198c26539a62d761e45af72cde570413d
  3. Affected versionversion=d4a44f0750bb9bf7c44c22444a482756b2344a79 <3761ae0d0e549f2acdaf11f49df4ed06d256b20f
  4. Affected versionversion=d4a44f0750bb9bf7c44c22444a482756b2344a79 <c4007596fbdabc29f858dc2e1990858a146b60b2
  5. Affected versionversion=d4a44f0750bb9bf7c44c22444a482756b2344a79 <fbf4daa6f4105e01fbd3868006f65c163365c1e3
  6. Affected versionversion=d4a44f0750bb9bf7c44c22444a482756b2344a79 <fe92c058199067ae90cf2a901ddf3c271893557a

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.0; version=d4a44f0750bb9bf7c44c22444a482756b2344a79 <1adf30f198c26539a62d761e45af72cde570413d; version=d4a44f0750bb9bf7c44c22444a482756b2344a79 <3761ae0d0e549f2acdaf11f49df4ed06d256b20f; version=d4a44f0750bb9bf7c44c22444a482756b2344a79 <c4007596fbdabc29f858dc2e1990858a146b60b2; version=d4a44f0750bb9bf7c44c22444a482756b2344a79 <fbf4daa6f4105e01fbd3868006f65c163365c1e3; version=d4a44f0750bb9bf7c44c22444a482756b2344a79 <fe92c058199067ae90cf2a901ddf3c271893557a
The Linux Kernel Organization · Linux Kernelversion=1da177e4c3f4 <1adf30f198c2; version=1da177e4c3f4 <3761ae0d0e54; version=1da177e4c3f4 <c4007596fbda; version=1da177e4c3f4 <fbf4daa6f410; version=1da177e4c3f4 <fe92c0581990

Published CVSS scores

7.1CISACVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-911Improper Update of Reference Count
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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