Mapserver · Mapserver · CVE-2026-33721
**Name of the Vulnerable Software and Affected Versions**
MapServer versions 4.2 through 8.6.0
**Description**
MapServer is a system for developing web-based GIS applications. A heap-buffer-overflow write in MapServer’s SLD (Styled Layer Descriptor) parser allows a remote, unauthenticated attacker to crash the MapServer process. This occurs by sending a crafted SLD with more than 100 Threshold elements inside a ColorMap/Categorize structure, commonly reachable via WMS GetMap with the `SLD BODY` parameter. The vulnerable component is the SLD parser.
**Recommendations**
Update to MapServer version 8.6.1 or later.