HOMEVULNERABILITIESCVE-2021-26236
HIGH

CVE-2021-26236

CWE-787Published: March 18, 2021· Updated: Jun 17, 2026

7.8
CVSS v3.1

Official Description

FastStone Image Viewer v.<= 7.5 is affected by a Stack-based Buffer Overflow at 0x005BDF49, affecting the CUR file parsing functionality (BITMAPINFOHEADER Structure, 'BitCount' file format field), that will end up corrupting the Structure Exception Handler (SEH). Attackers could exploit this issue to achieve code execution when a user opens or views a malformed/specially crafted CUR file.

NVD Source

Technical Analysis

CVE-2021-26236 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation does not require any privileges, though user interaction (Required) is needed, which slightly reduces the risk of mass automated attacks.

A successful exploit results in complete confidentiality breach (data exposure), full integrity compromise (data manipulation), availability disruption (denial of service), with a CVSS base score of 7.8.

From a weakness classification perspective (CWE-787): Out-of-bounds write vulnerabilities can lead to data corruption, crashes, or arbitrary code execution.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorLocal
Attack ComplexityLow
Privileges Req.None
User InteractionRequired
ScopeUnchanged
Impact
ConfidentialityHigh
IntegrityHigh
AvailabilityHigh
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected Vendors & Products

faststone1 product(s)
image viewer
Source: NVD CPE · 1 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

ADVISORYhttps://voidsec.com/advisories/cve-2021-26236-faststone-image-viewer-v-7-5-stack-based-buffer-overflow/
ADVISORYhttps://voidsec.com/fuzzing-faststone-image-viewer-cve-2021-26236
ADVISORYhttps://www.exploit-db.com/exploits/49660
ADVISORYhttps://voidsec.com/advisories/cve-2021-26236-faststone-image-viewer-v-7-5-stack-based-buffer-overflow/
ADVISORYhttps://voidsec.com/fuzzing-faststone-image-viewer-cve-2021-26236
ADVISORYhttps://www.exploit-db.com/exploits/49660

All References (6)

→
https://voidsec.com/advisories/cve-2021-26236-faststone-image-viewer-v-7-5-stack-based-buffer-overflow/Exploit · Third Party Advisory
→
https://voidsec.com/fuzzing-faststone-image-viewer-cve-2021-26236Exploit · Third Party Advisory
→
https://www.exploit-db.com/exploits/49660Exploit · Third Party Advisory · VDB Entry
→
https://voidsec.com/advisories/cve-2021-26236-faststone-image-viewer-v-7-5-stack-based-buffer-overflow/Exploit · Third Party Advisory
→
https://voidsec.com/fuzzing-faststone-image-viewer-cve-2021-26236Exploit · Third Party Advisory
→
https://www.exploit-db.com/exploits/49660Exploit · Third Party Advisory · VDB Entry

Quick Facts

CVE IDCVE-2021-26236
CVSS Score7.8 / 10
SeverityHIGH
WeaknessCWE-787
CISA KEVNo
Affected1 vendor(s)
PublishedMar 18, 2021

Related CVEs (CWE-787)

CVE-2018-3991
10.0
CVE-2004-0574
10.0
CVE-2012-0751
10.0
CVE-2018-17160
10.0
CVE-2019-6235
10.0
CVE-2026-4746
10.0

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2021-26236 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWatch. CVE data is provided under the NVD usage policy.
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