What is CVE-2020-35843?

CVE-2020-35843 is a medium-severity vulnerability in Faststone Image Viewer, classified under Out-of-bounds Write. CVSS score: 5.5/10. Published 2021-01-26.

How severe is CVE-2020-35843?

Medium severity. CVSS v3 base score is 5.5 out of 10.

Buffer overflow in Faststone Image Viewer

CVE-2020-35843

FastStone Image Viewer 7.5 has an out-of-bounds write (via a crafted image file) at FSViewer.exe+0x956e.

Vulnerability class: Buffer Overflow

Published 2021-01-26 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.5 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.007 (53.1th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 53rd percentile — 53.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Faststone Image Viewer — versions 7.5

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

twitter.com/DmitriyMelikov (Third Party Advisory)
github.com/DmitryMeD/pentesting/blob/main/FastStone Image Viewer 7.5.md (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2020-35843?: CVE-2020-35843 is a medium-severity vulnerability in Faststone Image Viewer, classified under Out-of-bounds Write. CVSS score: 5.5/10. Published 2021-01-26.
How severe is CVE-2020-35843?: Medium severity. CVSS v3 base score is 5.5 out of 10.