CVE-2017-12840
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 · uneditedA kernel driver, namely DLMFENC.sys, bundled with the DESLock+ client application 4.8.16 and earlier contains a locally exploitable heap based buffer overflow in the handling of an IOCTL message of type 0x0FA4204. The vulnerability is present due to the kernel driver failing to allocate sufficient memory on the kernel heap to contain a user supplied string as such the string is copied into a buffer of constant size (0x1000-bytes) and thus an overflow condition results. Access to the kernel driver is permitted through an obfuscated interface whereby bytes of user supplied message are "authenticated" via an obfuscation routine employing a linear equation.
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 confidenceThe DLMFENC.sys kernel driver bundled with DESLock+ client 4.8.16 and earlier contains a heap-based buffer overflow vulnerability triggered via IOCTL message type 0x0FA4204. The driver fails to allocate sufficient heap memory to contain a user-supplied string, instead copying directly into a fixed 0x1000-byte buffer, causing overflow. Access to the vulnerable code path is protected by an obfuscated interface requiring a specific linear equation-based authentication.
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<= 4.8.16CVSS 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:3.0/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 checksWork through these to decide whether this CVE applies to you.
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Verify DESLock+ client installationCheck for DESLock+ installation via Windows Programs and Features, or search for DESlock installation directory (typically C:\Program Files\DESlock+ or C:\Program Files (x86)\DESlock+)Affected if DESLock+ client is installed and version is 4.8.16 or lower
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Identify installed DESLock+ versionRight-click on DESLock+ in Programs and Features to view version, or check version info in the installation directoryAffected if Version displayed is 4.8.16 or any version lower (e.g., 4.8.15, 4.8.14, etc.)
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Locate DLMFENC.sys driver fileSearch for DLMFENC.sys in the Windows\System32\drivers folder or within the DESLock+ installation directoryAffected if DLMFENC.sys driver file exists on the system
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Check driver file versionRight-click DLMFENC.sys, select Properties, and view the File Version or Product Version fieldAffected if Driver version corresponds to DESLock+ 4.8.16 or earlier
The system is affected if DESLock+ client version 4.8.16 or earlier is installed and the DLMFENC.sys driver file is present on the system.
Generated from the published advisory. Verify against your own configuration.
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 dataApply vendor patch when available; otherwise remove or disable the DESLock+ driver, implement application whitelisting, or restrict access to the driver via endpoint controls to reduce attack surface.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA4.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $6,176.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2017-12840 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2017-12840 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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