dbcve.org
EfibootguardApplication · Siemens

CVE-2023-39950

MEDIUM · 5.2 CVSS v3.1 Published 2023-08-14
Fix available
A fix is available. Upgrade to 0.15 or later.
See remediation →
57/100
Remediation priority · Elevated
No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
efibootguard is a simple UEFI boot loader with support for safely switching between current and updated partition sets. Insufficient or missing validation and sanitization of input from untrustworthy bootloader environment files can cause crashes and probably also code injections into `bg_setenv`) or programs using `libebgenv`. This is triggered when the affected components try to modify a manipulated environment, in particular its user variables. Furthermore, `bg_printenv` may crash over invalid read accesses or report invalid results. Not affected by this issue is EFI Boot Guard's bootloader EFI binary. EFI Boot Guard release v0.15 contains required patches to sanitize and validate the bootloader environment prior to processing it in userspace. Its library and tools should be updated, so should programs statically linked against it. An update of the bootloader EFI executable is not required. The only way to prevent the issue with an unpatched EFI Boot Guard version is to avoid accesses to user variables, specifically modifications to them.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

efibootguard contains insufficient validation of bootloader environment file input, allowing malformed user variables to cause crashes in bg_setenv and bg_printenv, and potentially enable code injection through bg_setenv or programs using libebgenv. The vulnerability exists in userspace tools and library components, not in the EFI bootloader binary itself.

MitigationUpdate to EFI Boot Guard release v0.15 or later which contains patches to sanitize and validate the bootloader environment prior to processing. Alternatively, avoid modifications to user variables in unpatched versions.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
EfibootguardApplication
Affected:< 0.15

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Physical
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
Low

CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:L

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check efibootguard version
    Query the installed package version using the system package manager (dpkg -l efibootguard, rpm -q efibootguard, or similar) or run 'bg_setenv --version' or 'bg_printenv --version' if available
    Affected if The installed version is below 0.15
  2. Identify userspace tools
    Locate the bg_setenv and bg_printenv binaries on the system using 'which bg_setenv bg_printenv' or 'find /usr -name bg_setenv -o -name bg_printenv'
    Affected if These tools exist on the system and belong to an efibootguard version < 0.15
  3. Check for libebgenv library
    Search for libebgenv shared library using 'ldconfig -p | grep ebgenv' or 'find /usr -name *ebgenv*'
    Affected if Programs using libebgenv to manipulate bootloader environment are in use and the library version is < 0.15
  4. Locate bootloader environment file
    Identify the EFI Boot Guard environment file path, typically at /boot/efi/EFI/*/bootenv or as specified in system documentation
    Affected if The environment file exists and is readable by the userspace tools, indicating potential for malformed variable processing

A system is affected if efibootguard userspace tools (bg_setenv, bg_printenv) or libebgenv with version below 0.15 are installed and used to handle bootloader environment variables.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.15 or later
Fixed in 0.15
Interim mitigation

Update to EFI Boot Guard release v0.15 or later which contains patches to sanitize and validate the bootloader environment prior to processing. Alternatively, avoid modifications to user variables in unpatched versions.

Recommended fix High confidence

v0.15

  1. Identify all systems running efibootguard versions prior to 0.15
  2. Upgrade efibootguard to version 0.15 or later using the package manager or recompiling from source
  3. If using libebgenv library or tools like bg_setenv or bg_printenv, rebuild them against the updated library
  4. Verify that the upgraded version is running by checking the installed version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Efibootguard Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing6.0 h
  • Review / QA3.0 h
25.0 hours of engineering $4,400
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $7,040.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2023-39950 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-39950 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data