CVE-2021-26237
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 · uneditedFastStone Image Viewer <= 7.5 is affected by a user mode write access violation at 0x00402d7d, triggered when a user opens or views a malformed CUR file that is mishandled by FSViewer.exe. Attackers could exploit this issue for a Denial of Service (DoS) or possibly to achieve code execution.
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 · moderate confidenceFastStone Image Viewer <= 7.5 contains a user-mode write access violation vulnerability in FSViewer.exe when parsing malformed CUR (Windows cursor) files. The vulnerability occurs due to improper handling of CUR file structure, allowing an attacker to trigger a write to an arbitrary memory location, potentially leading to denial of service or code execution.
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<= 7.5CVSS 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
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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 FastStone Image Viewer installationSearch for FSViewer.exe on the system, typically found in C:\Program Files\FastStone Image Viewer\ or C:\Program Files (x86)\FastStone Image Viewer\Affected if FSViewer.exe is found on the system
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Determine installed versionRight-click FSViewer.exe, select Properties, then check the Details tab for the Product Version field. Alternatively, launch the application and go to Help > About FastStone Image ViewerAffected if The version displayed is 7.5 or any version lower than 7.5
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Identify CUR file handling usageCheck if the application is configured to open .cur files, or review recent file history for .cur file access. Inspect File > Open file type filters or File > Associations settingsAffected if The application is used to open or preview CUR (cursor) files from untrusted sources
The environment is affected if FastStone Image Viewer version 7.5 or lower is installed and users open malformed CUR files with it.
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 dataAvoid opening untrusted or malformed CUR files in FastStone Image Viewer. Update to a patched version when released by the vendor. Consider using alternative image viewers for untrusted cursor files.
- Consultation3.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-26237 — 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-2021-26237 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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