CVE-2021-38993

Local denial of service via undisclosed smbcd flaw

Published Feb 25, 2022 · Updated Sep 17, 2024

Denial of service in IBM AIX 7.1 through 7.3 and VIOS 3.1 allows local users to disrupt the smbcd daemon through local access. IBM has not published the vulnerable code path or the operation that mishandles input in smbcd. Exploitation requires a non-privileged local account, and the documented consequence is limited to smbcd availability loss.

CVSS severity6.2
Medium
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

Denial of service in IBM AIX 7.1 through 7.3 and VIOS 3.1 allows local users to disrupt the smbcd daemon through local access. IBM has not published the vulnerable code path or the operation that mishandles input in smbcd. Exploitation requires a non-privileged local account, and the documented consequence is limited to smbcd availability loss.

The record

CVE
CVE-2021-38993
Published
Feb 25, 2022
Updated
Sep 17, 2024
Vendor
IBM
Product
AIX
Classifications
T1499
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 25, 2022CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record 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=7.1
  2. Affected versionversion=7.2
  3. Affected versionversion=7.3

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

IBM · AIXversion=7.1; version=7.2; version=7.3
IBM · PowerVM Virtual I/O Serverversion=3.1

Published CVSS scores

6.2IBMCVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:N/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.

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)
Vectorlocal
Privilegesauthenticated
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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