CVE-2021-46968

Memory exhaustion via unbalanced hot-unplug references

Published Feb 27, 2024 · Updated May 11, 2026

Memory leak in the s390 zcrypt subsystem in Linux kernel 5.10 allows attackers to retain kernel memory by hot-unplugging cards or queues. The card and queue initialization paths leave each embedded kref at its initial count, while unregistering fails to drop that reference to zero and release the object. Reachability requires an s390 system with zcrypt devices and authority to hot-unplug a card or queue; repeated removals retain allocations until kernel memory is exhausted.

CVSS severityUnavailable
Unscored
EPSS probability0.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory leak in the s390 zcrypt subsystem in Linux kernel 5.10 allows attackers to retain kernel memory by hot-unplugging cards or queues. The card and queue initialization paths leave each embedded kref at its initial count, while unregistering fails to drop that reference to zero and release the object. Reachability requires an s390 system with zcrypt devices and authority to hot-unplug a card or queue; repeated removals retain allocations until kernel memory is exhausted.

The record

CVE
CVE-2021-46968
Published
Feb 27, 2024
Updated
May 11, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1499
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Feb 27, 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=29c2680fd2bf3862ff5cf2957f198512493156f9 <026499a9c2e002e621ad568d1378324ae97e5524
  2. Affected versionversion=29c2680fd2bf3862ff5cf2957f198512493156f9 <055a063a18bcd19b93709e3eac8078d6b2f04599
  3. Affected versionversion=29c2680fd2bf3862ff5cf2957f198512493156f9 <70fac8088cfad9f3b379c9082832b4d7532c16c2
  4. Affected versionversion=29c2680fd2bf3862ff5cf2957f198512493156f9 <971dc8706cee47393d393905d294ea47e39503d3
  5. Affected versionversion=5.10

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linuxversion=29c2680fd2bf3862ff5cf2957f198512493156f9 <026499a9c2e002e621ad568d1378324ae97e5524; version=29c2680fd2bf3862ff5cf2957f198512493156f9 <055a063a18bcd19b93709e3eac8078d6b2f04599; version=29c2680fd2bf3862ff5cf2957f198512493156f9 <70fac8088cfad9f3b379c9082832b4d7532c16c2; version=29c2680fd2bf3862ff5cf2957f198512493156f9 <971dc8706cee47393d393905d294ea47e39503d3; version=5.10

Published CVSS scores

No CVSS assessment is available in this record.

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

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

Weakness, pattern, technique

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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