CVE-2019-9896
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 · uneditedIn PuTTY versions before 0.71 on Windows, local attackers could hijack the application by putting a malicious help file in the same directory as the executable.
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 confidenceA binary planting vulnerability in PuTTY before version 0.71 on Windows allows local attackers to execute arbitrary code by placing a malicious help file (.chm or .hlp) in the same directory as the PuTTY executable. When PuTTY runs, it loads the malicious help file instead of the legitimate one from its installation directory.
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< 0.71= 15.0= 15.0CVSS 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 checksWork through these to decide whether this CVE applies to you.
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Locate PuTTY executable and identify its versionFind putty.exe on the system (common paths: C:\Program Files\PuTTY\putty.exe, C:\Program Files (x86)\PuTTY\putty.exe). Right-click the executable, select Properties, and check the Version tab or File version field. Alternatively, run 'putty.exe -V' or 'putty.exe --version' from command prompt.Affected if The reported version is less than 0.71 (for example, 0.70, 0.68, or earlier)
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Determine the directory from which PuTTY is launchedObserve the current working directory when launching PuTTY. If launching via shortcut, right-click the shortcut and check the 'Start in' field. Identify if this directory is in user-downloads, shared network folders, or other locations writable by untrusted users.Affected if PuTTY is launched from or runs in a directory that is writable by untrusted users (e.g., Downloads folder, shared network drive, desktop)
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Check for unexpected help files in the PuTTY launch directoryInspect the directory from which PuTTY is run. Look for files with .chm or .hlp extensions (e.g., putty.chm, putty.hlp, PuTTY_help.chm) that are not part of the official PuTTY installation.Affected if A .chm or .hlp file exists in the same directory as the PuTTY executable and was not placed there by the official installer
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Compare the help file path loaded by PuTTYRun PuTTY with Process Monitor (ProcMon) from Sysinternals to trace file accesses. Filter for PuTTY.exe accessing .chm or .hlp files. Verify whether it loads the file from its installation directory (e.g., C:\Program Files\PuTTY\putty.chm) or from the current working directory.Affected if PuTTY loads a help file from the current working directory rather than from its installation directory
A system is affected if PuTTY version is below 0.71 AND PuTTY is run from or can have its working directory controlled by an untrusted user who can place a malicious .chm or .hlp file.
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 data0.71
Update PuTTY to version 0.71 or later. Additionally, ensure PuTTY is run from a directory that is not writable by untrusted users (avoid running from user-downloads or shared folders).
- Consultation1.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-9896 — 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-2019-9896 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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