CVE-2026-39031
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 · uneditedLansweeper lsrunase 2.0 and lsencrypt 2.0 use RC4 encryption with a hardcoded 142-byte static key array to encrypt credentials. An 8-character prefix is stored in cleartext alongside the ciphertext. This allows an attacker with local access to recover any encrypted password to plaintext using a single SHA-1 hash and RC4 decryption operation, with no brute force required.
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 Lansweeper lsrunase and lsencrypt tools (v2.0) use the broken RC4 stream cipher with a hardcoded 142-byte static key to encrypt sensitive credentials. An 8-character cleartext prefix stored alongside the ciphertext enables trivial decryption via a single SHA-1 hash operation—bypassing brute force entirely.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
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
- None
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
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.
-
Identify Lansweeper lsrunase and lsencrypt installationSearch for lsrunase.exe, lsencrypt.exe, or Lansweeper installation directories on the system. Common paths include C:\Program Files\Lansweeper or C:\Program Files (x86)\Lansweeper.Affected if The lsrunase.exe or lsencrypt.exe binaries from Lansweeper version 2.0 are found on the system.
-
Determine the installed version of lsrunase or lsencryptRight-click on lsrunase.exe or lsencrypt.exe, select Properties, and check the File Version field under the Details tab. Alternatively, run 'lsrunase.exe /?' or 'lsencrypt.exe /?' to display version information.Affected if The version displayed is 2.0.x or the tool is confirmed to be the v2.0 release.
-
Check for presence of encrypted credential files or configurationsLook for configuration files, credential stores, or database entries that contain RC4-encrypted data. Search for files with patterns like *.config, *.xml, or database files in the Lansweeper data directories that store encrypted credentials.Affected if Encrypted credential data exists in configuration files or databases used by Lansweeper.
-
Identify the 8-character prefix in encrypted dataExamine any encrypted credential strings found. The weak RC4 implementation uses an 8-character cleartext prefix stored alongside the ciphertext. Look for any 8-character alphanumeric strings preceding or associated with encrypted credential blobs.Affected if An 8-character cleartext prefix is found stored alongside ciphertext in Lansweeper credential storage.
A system is affected if Lansweeper lsrunase or lsencrypt version 2.0 is installed and contains encrypted credentials using the RC4 scheme with an 8-character prefix.
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 dataReplace the hardcoded RC4 encryption with modern authenticated encryption (e.g., AES-256-GCM) using properly generated per-instance keys; migrate all existing encrypted credentials using the new scheme.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-39031 — 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-2026-39031 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
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.
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.
- 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