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CVE-2026-33721

MapServer has heap buffer overflow in SLD `Categorize` Threshold parsing

Published: Mar 27, 2026Updated: Apr 17, 2026 Sources: CVE List NVDCWE-787
NVD MITRE
5.3CVSSMEDIUM
EPSS Score
0.6%
Top 53.9%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Workaround Only

Description

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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:NA:L
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:LAvailability
Low
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Weaknesses

CWE-787

Affected Products

mapserverosgeo
Mixed
OSS Libraries / generic-library
MapServerMapServer
On-prem
Cloud & SaaS / cloud-platform
osgeooss-projectOSS Librariesaka gdal, geoserver, mapserver
mapserveross-projectCloud & SaaSaka mapserver

Attack Graph

Products CVE Techniques Tactics

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Exploitability

Workaround Available

MITRE ATT&CK

2 techniques
Initial Access
Privilege Escalation
View detailed technique mapping

References

https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1
github.com
https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp
github.com
https://lists.debian.org/debian-lts-announce/2026/04/msg00017.html
lists.debian.org

Timeline

Published
Mar 27, 2026
Last Updated
Apr 17, 2026

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