CVE-2023-39538

Privilege escalation via zero-size BMP allocation

Published Dec 6, 2023 · Updated Feb 25, 2026

Memory corruption in the Aptio V BIOS BMP parser before BKS_5.34 allows local privileged users to escalate privileges via a crafted logo. The DXE image-decoding path accepts a crafted BMP with a zero allocation size, then continues processing and writes beyond the allocated buffer. Exploitation requires high-privileged local access to replace the boot logo on an affected x86 platform and can execute code in the preboot firmware context.

CVSS severity7.5
High
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 corruption in the Aptio V BIOS BMP parser before BKS_5.34 allows local privileged users to escalate privileges via a crafted logo. The DXE image-decoding path accepts a crafted BMP with a zero allocation size, then continues processing and writes beyond the allocated buffer. Exploitation requires high-privileged local access to replace the boot logo on an affected x86 platform and can execute code in the preboot firmware context.

The record

CVE
CVE-2023-39538
Published
Dec 6, 2023
Updated
Feb 25, 2026
Vendor
American Megatrends International
Product
Aptio V
Classifications
CWE-434, CWE-20, T1068
Attack vector
local
Privileges
admin

Timeline

How it unfolded

  1. Dec 6, 2023CVE publishedPublication date reported by the CVE source.
  2. Feb 25, 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=BKS_5.0 <BKS_5.34

What conditions does exploitation require?

Attack vectorlocal
Required privilegesadmin

What is affected?

American Megatrends International · Aptio Vversion=BKS_5.0 <BKS_5.34

Published CVSS scores

7.8NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.5AMICVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:C/C:H/I:H/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
Privilegesadmin
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-434Unrestricted Upload of File with Dangerous Type
CWE-20Improper Input Validation
T1068Exploitation for Privilege Escalation

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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