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Image ViewerApplication · Faststone

CVE-2021-26233

HIGH · 7.8 CVSS v3.1 Published 2021-03-18
Fix available
A fix is available. Upgrade to after 7.5 or later.
See remediation →
81/100
Remediation priority · High
No privileges

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
FastStone Image Viewer <= 7.5 is affected by a user mode write access violation near NULL at 0x005bdfcb, 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 confidence

FastStone Image Viewer versions 7.5 and prior contain a memory corruption vulnerability when parsing malformed CUR (Windows cursor) files. The application experiences a user mode write access violation near NULL pointer address 0x005bdfcb, indicating a null pointer dereference with an offset during CUR file parsing in FSViewer.exe. This can cause application crash (DoS) and potentially allow arbitrary code execution.

MitigationAvoid opening untrusted or malformed CUR files with FastStone Image Viewer. Update to a patched version if released by FastStone, or migrate to an alternative image viewer that receives timely security updates.

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
Image ViewerApplication
Affected:<= 7.5

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
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 checks

Work through these to decide whether this CVE applies to you.

  1. Confirm FastStone Image Viewer is installed
    Search for FSViewer.exe on the system or check the installed programs list for FastStone Image Viewer
    Affected if FastStone Image Viewer is present on the system
  2. Determine the installed version
    Right-click on FSViewer.exe, select Properties, and check the Details tab for the File Version, or use the application's About/Help menu to view version information
    Affected if The installed version is 7.5 or any version prior to 7.5
  3. Verify CUR file handling is possible
    Attempt to open a CUR file (Windows cursor) in FastStone Image Viewer to confirm the application can parse this file type
    Affected if The application can open CUR files and the version is 7.5 or lower

If FastStone Image Viewer version 7.5 or prior is installed and can be used to open CUR files, the environment is affected by this vulnerability.

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
Upgrade available Upgrade to a release after 7.5
Interim mitigation

Avoid opening untrusted or malformed CUR files with FastStone Image Viewer. Update to a patched version if released by FastStone, or migrate to an alternative image viewer that receives timely security updates.

Fix this in Image Viewer Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $910
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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-2021-26233 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