CVE-2021-26234

Process crash via malformed CUR file parsing

Published Mar 18, 2021 · Updated Aug 3, 2024

Out-of-bounds write in FastStone Image Viewer 7.5 and earlier allows attackers to crash FSViewer.exe through a malformed CUR file. FSViewer.exe mishandles crafted cursor data and performs an invalid user-mode write at address 0x00402d8a while opening or viewing the file. A user must open or preview the file; a process crash is confirmed, while code execution is reported only as a possibility.

CVSS severity7.8
High
EPSS probability1.06%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in FastStone Image Viewer 7.5 and earlier allows attackers to crash FSViewer.exe through a malformed CUR file. FSViewer.exe mishandles crafted cursor data and performs an invalid user-mode write at address 0x00402d8a while opening or viewing the file. A user must open or preview the file; a process crash is confirmed, while code execution is reported only as a possibility.

The record

CVE
CVE-2021-26234
Published
Mar 18, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-787, T1204.002, T1203
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 18, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.8NIST NVDCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NIST NVDAV:N/AC:M/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1204.002User Execution Malicious File
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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