CVE-2023-39950

Code injection and crashes via malformed user variables

Published Aug 14, 2023 · Updated Oct 1, 2024

Improper input validation in EFI Boot Guard before 0.15 allows physically proximate attackers to crash or inject code into userspace tools. bg_setenv and libebgenv process manipulated user-variable records without adequately validating their structure, while bg_printenv performs invalid reads. Exploitation requires control of an environment file later processed by an affected userspace component; the UEFI bootloader binary is unaffected.

CVSS severity6.1
Medium
EPSS probability0.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in EFI Boot Guard before 0.15 allows physically proximate attackers to crash or inject code into userspace tools. bg_setenv and libebgenv process manipulated user-variable records without adequately validating their structure, while bg_printenv performs invalid reads. Exploitation requires control of an environment file later processed by an affected userspace component; the UEFI bootloader binary is unaffected.

The record

CVE
CVE-2023-39950
Published
Aug 14, 2023
Updated
Oct 1, 2024
Vendor
Siemens AG
Product
EFI Boot Guard
Classifications
CWE-20, T1565.001
Attack vector
physical
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 14, 2023CVE publishedPublication date reported by the CVE source.
  2. Oct 1, 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=< 0.15

What conditions does exploitation require?

Attack vectorphysical
Required privilegesunauthenticated

What is affected?

Siemens AG · EFI Boot Guardversion=< 0.15

Published CVSS scores

5.2NIST NVDCVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L
6.1GitHub, Inc.CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:L

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)
Vectorphysical
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-20Improper Input Validation
T1565.001Data Manipulation: Stored Data Manipulation

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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