How severe is CVE-2021-26236?

CVE-2021-26236 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-26236 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26236?

CVE-2021-26236 affects Faststone Image Viewer. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-26236?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-26236 published?

CVE-2021-26236 was published on 2021-03-18 and last updated on 2026-06-17.

CVE-2021-26236

CVE-2021-26236 is a high-severity vulnerability in Faststone Image Viewer with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: High (CVSS 3.x base score 7.8)
CVSS v2: 6.8
EPSS exploit prediction: 2% (78th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Faststone Image Viewer
Published: 2021-03-18
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-26236?: 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.
How severe is CVE-2021-26236?: CVE-2021-26236 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-26236 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (78th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26236?: CVE-2021-26236 affects Faststone Image Viewer. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-26236?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-26236 published?: CVE-2021-26236 was published on 2021-03-18 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:faststone:image_viewer:*:*:*:*:*:*:*:*

More vulnerabilities in Faststone Image Viewer

CVE-2022-36947 — Critical (CVSS 9.8): Unsafe Parsing of a PNG tRNS chunk in FastStone Image Viewer through 7.5 results in a stack buffer overflow.
CVE-2007-1942 — Critical (CVSS 9.3): Integer overflow in FastStone Image Viewer 2.9 allows context-dependent attackers to cause a denial of service and…
CVE-2024-9114 — High (CVSS 7.8): FastStone Image Viewer GIF File Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability. This vulnerability…
CVE-2024-9113 — High (CVSS 7.8): FastStone Image Viewer TGA File Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability. This vulnerability…
CVE-2024-9112 — High (CVSS 7.8): FastStone Image Viewer PSD File Parsing Out-Of-Bounds Write Remote Code Execution Vulnerability. This vulnerability…
CVE-2021-26237 — High (CVSS 7.8): FastStone Image Viewer <= 7.5 is affected by a user mode write access violation at 0x00402d7d, triggered when a user…

All CVEs affecting Faststone Image Viewer →

Other CWE-787 (Out-of-bounds Write) vulnerabilities

CVE-2026-42369 — Critical (CVSS 10.0): GV-VMS V20 is a Video Monitoring Software used to gather the feeds of many surveillance cameras and manage other…
CVE-2026-4746 — Critical (CVSS 10.0): Out-of-bounds Write vulnerability in timeplus-io proton (base/poco/Foundation/src‎ modules). This vulnerability is…
CVE-2025-43300 — Critical (CVSS 10.0): An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in iOS 15.8.5 and iPadOS…
CVE-2025-24201 — Critical (CVSS 10.0): An out-of-bounds write issue was addressed with improved checks to prevent unauthorized actions. This issue is fixed in…
CVE-2024-42479 — Critical (CVSS 10.0): llama.cpp provides LLM inference in C/C++. The unsafe `data` pointer member in the `rpc_tensor` structure can cause…
CVE-2024-39791 — Critical (CVSS 10.0): Stack-based buffer overflow vulnerabilities affecting Vonets industrial wifi bridge relays and wifi bridge…

Browse all CWE-787 (Out-of-bounds Write) vulnerabilities →