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CVE Record

CVE-2021-38993: IBM AIX 7.1, 7.2, 7.3, and VIOS 3.1 could allow a non-privileged local user to exploit a vulnerability in t...

IBM AIX 7.1, 7.2, 7.3, and VIOS 3.1 could allow a non-privileged local user to exploit a vulnerability in the smbcd daemon to cause a denial of service. IBM X-Force ID: 212962.

MediumCVSS 6.2Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2021-38993 is a local denial-of-service issue in IBM AIX and VIOS. A non-privileged local user could abuse the smbcd daemon and disrupt availability. It does not claim data theft or data modification, but business systems relying on affected AIX or VIOS hosts could experience service interruption.

Executive priority

Prioritize remediation for shared, production, or business-critical AIX and VIOS systems with many local users. This is not described as a remote compromise risk, but it can still affect service availability on important infrastructure.

Technical view

IBM reports a vulnerability in the smbcd daemon affecting AIX 7.1, 7.2, 7.3, and VIOS 3.1. The CVSS 3.0 score is 6.2 with local attack vector, low complexity, no user interaction, no confidentiality or integrity impact, and high availability impact.

Likely exposure

Exposure is limited to IBM AIX 7.1, 7.2, 7.3, and VIOS 3.1 systems where a local user can reach the vulnerable component. Internet-facing exposure is not indicated by the CVSS vector or source description.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation. The CVSS vector lists exploit maturity as unproven. Treat this as a local availability risk until IBM or another cited source indicates exploitation in the wild.

Researcher notes

Key constraints are local attack vector and availability-only impact. Sources do not provide exploit details, affected fix packs, or configuration-specific exposure beyond smbcd on listed AIX and VIOS versions. Use IBM guidance for exact remediation mapping.

Mitigation direction

  • Review IBM advisory node 6559320 for fixed levels and official remediation.
  • Apply IBM-provided fixes or service updates for affected AIX and VIOS versions.
  • Limit local interactive access to trusted users where operationally possible.
  • Monitor affected hosts for smbcd crashes or unexpected service restarts.

Validation and detection

  • Inventory AIX and VIOS hosts and identify versions 7.1, 7.2, 7.3, and 3.1.
  • Check whether IBM advisory remediation has been applied on each affected host.
  • Confirm whether smbcd is present and operational on in-scope systems.
  • Review availability monitoring for recent smbcd-related instability or outages.
Prepared
Confidence
high
Sources
4

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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CVE-2021-38993 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
6.2 (3.0)
Known Exploited
No
Published

Vector: CVSS:3.0/AV:L/S:U/C:N/PR:N/A:H/AC:L/I:N/UI:N/RL:O/E:U/RC:C

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
0Timeline events
0ADP providers
3Source links

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
6.2CVSS 3.0MediumCVSS:3.0/AV:L/S:U/C:N/PR:N/A:H/AC:L/I:N/UI:N/RL:O/E:U/RC:C2.53.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.0 score

6.2Medium
CVSS 3.0 vector shape for CVE-2021-38993Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.0/AV:L/S:U/C:N/PR:N/A:H/AC:L/I:N/UI:N/RL:O/E:U/RC:C

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

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
IBMVIOS3.1Listed
IBMAIX7.1, 7.2, 7.3Listed
Weakness

CWE details

No CWE listed

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