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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Privileges Required
None
No privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
None
No data modification
Availability
High
Complete denial of service
CVSS Vector v3.1
Weakness Type (CWE)
Vulnerable Products 1
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Osgeo Mapserver
cpe:2.3:a:osgeo:mapserver:*:*:*:*:*:*:*:*
|
4.2.0
|
8.6.1
|
References 3
https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1
security-advisories@github.com
https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp
security-advisories@github.com
https://lists.debian.org/debian-lts-announce/2026/04/msg00017.html
af854a3a-2127-422b-91ae-364da2661108