Heap Buffer Overflow in MapServer Affects Web-based GIS Applications
CVE-2026-33721

5.3MEDIUM

Key Information:

Vendor

Mapserver

Status
Mapserver
Vendor
CVE Published:
27 March 2026

What is CVE-2026-33721?

MapServer, a popular framework for creating web-based Geographic Information System (GIS) applications, contains a vulnerability in its SLD parser. This flaw allows a remote, unauthenticated attacker to exploit the system by sending a specially crafted SLD containing more than 100 Threshold elements within a ColorMap/Categorize structure. Such an attack can lead to a crash of the MapServer process, potentially disrupting service. Mitigation is available in version 8.6.1, which addresses this issue by refining the parsing routine. It is crucial for users of the affected versions to upgrade to ensure system integrity and availability.

Affected Version(s)

MapServer >= 4.2, < 8.6.1

References

https://github.com/MapServer/MapServer/security/advisorie...
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https://github.com/MapServer/MapServer/releases/tag/rel-8...
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CVSS V3.1

Score:
5.3
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.