What is CVE-2026-33721?

CVE-2026-33721 is a medium-severity vulnerability in Mapserver, classified under Out-of-bounds Write. CVSS score: 5.3/10. Published 2026-03-27.

How severe is CVE-2026-33721?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Buffer overflow in Mapserver

CVE-2026-33721

MapServer is a system for developing web-based GIS applications. Starting in version 4.2 and prior to version 8.6.1, a heap-buffer-overflow write in MapServer’s SLD (Styled Layer Descriptor) parser lets a remote, unauthenticated attacker c…

Vulnerability class: Buffer Overflow

EPSS: 0.003 (53.7th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

Affected products

Mapserver — versions >= 4.2, < 8.6.1

Weakness classification (CWE)

CWE-787 — Out-of-bounds Write

References

https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp (x_refsource_CONFIRM)
https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1 (x_refsource_MISC)

Frequently asked questions

What is CVE-2026-33721?: CVE-2026-33721 is a medium-severity vulnerability in Mapserver, classified under Out-of-bounds Write. CVSS score: 5.3/10. Published 2026-03-27.
How severe is CVE-2026-33721?: Medium severity. CVSS v3 base score is 5.3 out of 10.