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Linux ProtectionApplication · F Secure

CVE-2023-43766

HIGH · 7.8 CVSS v3.1 Published 2023-09-22
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
80/100
Remediation priority · High
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
Certain WithSecure products allow Local privilege escalation via the lhz archive unpack handler. This affects WithSecure Client Security 15, WithSecure Server Security 15, WithSecure Email and Server Security 15, WithSecure Elements Endpoint Protection 17 and later, WithSecure Client Security for Mac 15, WithSecure Elements Endpoint Protection for Mac 17 and later, Linux Security 64 12.0 , Linux Protection 12.0, and WithSecure Atlant (formerly F-Secure Atlant) 1.0.35-1.

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

A local privilege escalation vulnerability exists in the lhz archive unpack handler of multiple WithSecure endpoint protection products. An attacker with local access to an affected system can exploit this vulnerability to gain elevated administrator or root privileges, potentially compromising the entire system.

MitigationApply the vendor-supplied security updates or patches to all affected WithSecure products. Since this requires local access, ensure proper access controls and monitoring for untrusted local users.

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
Linux ProtectionApplication
Affected:= 12.0
Linux Security 64Application
Affected:= 12.0
AtlantApplication
Affected:= 1.0.35-1
Client SecurityApplication
Affected:= 15.00
Elements Endpoint ProtectionApplication
Affected:>= 17.0
Email And Server SecurityApplication
Affected:= 15.00
Server SecurityApplication
Affected:= 15.00

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
Local
Complexity
Low
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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. Identify installed WithSecure products
    Run 'rpm -qa | grep -i f-secure' or 'dpkg -l | grep -i f-secure' or check /opt/f-secure for product directories. For Linux, also check /var/opt/f-secure for common install paths.
    Affected if Any WithSecure product from the affected list is installed
  2. Check product version
    For F-Secure Linux Protection/Security 64: run 'fssp --version' or check /var/opt/f-secure/common/version. For Client Security/Server Security: check Windows registry or the product's built-in version info. Compare your installed version against the affected ranges: =12.0, =1.0.35-1, =15.00, >=17.0.
    Affected if Installed version exactly matches or falls within the affected version ranges listed in the CVE
  3. Verify lhz archive handler is active
    Check if the lhz unpack handler module is loaded or enabled. Look for files related to lhz handling in the product's module directories, or check product logs for lhz archive processing activity. On Linux, examine /opt/f-secure/*/modules/ for lhz-related components.
    Affected if The lhz archive unpack handler module is present and enabled in the product configuration
  4. Confirm local user context
    Review system for local user accounts. This vulnerability requires an attacker to have local access to the system. Check /etc/passwd for untrusted local accounts and review access controls.
    Affected if Untrusted local users or accounts exist on the system with access to the WithSecure product

The system is affected if a WithSecure product listed in the CVE is installed with an affected version (=12.0, =1.0.35-1, =15.00, or >=17.0) and the lhz archive unpack handler is enabled.

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.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Apply the vendor-supplied security updates or patches to all affected WithSecure products. Since this requires local access, ensure proper access controls and monitoring for untrusted local users.

Fix this in Linux Protection Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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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-2023-43766 in production — separate from our analysis above.

No notes yet

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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