Bug 2452066 (CVE-2026-33721)

Summary: CVE-2026-33721 MapServer: MapServer: Denial of Service via crafted Styled Layer Descriptor
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in MapServer, a system for developing web-based Geographic Information System (GIS) applications. A remote, unauthenticated attacker can exploit a heap-buffer-overflow vulnerability by sending a specially crafted Styled Layer Descriptor (SLD) with an excessive number of Threshold elements. This can cause the MapServer process to crash, leading to a Denial of Service (DoS).
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Bug Depends On: 2452126, 2452127    
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Description OSIDB Bzimport 2026-03-27 01:02:05 UTC
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.