Vulnerability Report

CVE-2026-33721

Title: MapServer SLD Parser Heap-Buffer-Overflow DoS

Memory Corruption

Proof Of Concept

No public PoC currently indexed for CVE-2026-33721.

CWE Category CWE-787

Published Date Mar 27, 2026

Modified Date Apr 17, 2026

Exploit Status Not Found

Score 5.3 CVSS v3.1

Exploit Probability (EPSS)

0.30%

Vulnerability Summary

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 crash the MapServer process by sending a crafted SLD with more than 100 Threshold elements inside a ColorMap/Categorize structure (commonly reachable via WMS GetMap with SLD_BODY). Version 8.6.1 patches the issue.

Impacted Vendors

university_of_minnesota 1

osgeo 1

Reference Links

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

CVSS v3.1

Source Entity [email protected]

Severity MEDIUM

5.3

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L