Vulnerability Details CVE-2026-33721
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.001
EPSS Ranking 21.9%
CVSS Severity
CVSS v3 Score 5.3
References
Products affected by CVE-2026-33721
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cpe:2.3:a:osgeo:mapserver:4.10.0
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cpe:2.3:a:osgeo:mapserver:4.10.1
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cpe:2.3:a:osgeo:mapserver:4.10.2
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cpe:2.3:a:osgeo:mapserver:4.10.3
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cpe:2.3:a:osgeo:mapserver:4.10.4
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cpe:2.3:a:osgeo:mapserver:4.10.5
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cpe:2.3:a:osgeo:mapserver:4.2.0
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cpe:2.3:a:osgeo:mapserver:4.2.1
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cpe:2.3:a:osgeo:mapserver:4.2.2
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cpe:2.3:a:osgeo:mapserver:4.2.3
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cpe:2.3:a:osgeo:mapserver:4.2.4
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cpe:2.3:a:osgeo:mapserver:4.2.5
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cpe:2.3:a:osgeo:mapserver:4.4.0
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cpe:2.3:a:osgeo:mapserver:4.4.1
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cpe:2.3:a:osgeo:mapserver:4.4.2
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cpe:2.3:a:osgeo:mapserver:4.6.0
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cpe:2.3:a:osgeo:mapserver:4.6.1
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cpe:2.3:a:osgeo:mapserver:4.6.2
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cpe:2.3:a:osgeo:mapserver:4.8.0
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cpe:2.3:a:osgeo:mapserver:4.8.1
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cpe:2.3:a:osgeo:mapserver:4.8.2
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cpe:2.3:a:osgeo:mapserver:4.8.3
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cpe:2.3:a:osgeo:mapserver:4.8.4
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cpe:2.3:a:osgeo:mapserver:5.0.0
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cpe:2.3:a:osgeo:mapserver:5.2
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cpe:2.3:a:osgeo:mapserver:5.2.0
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cpe:2.3:a:osgeo:mapserver:5.2.1
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cpe:2.3:a:osgeo:mapserver:5.4
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cpe:2.3:a:osgeo:mapserver:5.4.0
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cpe:2.3:a:osgeo:mapserver:5.4.1
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cpe:2.3:a:osgeo:mapserver:5.4.2
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cpe:2.3:a:osgeo:mapserver:5.6.0
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cpe:2.3:a:osgeo:mapserver:5.6.1
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cpe:2.3:a:osgeo:mapserver:5.6.2
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cpe:2.3:a:osgeo:mapserver:5.6.3
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cpe:2.3:a:osgeo:mapserver:5.6.4
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cpe:2.3:a:osgeo:mapserver:5.6.5
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cpe:2.3:a:osgeo:mapserver:5.6.6
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cpe:2.3:a:osgeo:mapserver:5.6.7
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cpe:2.3:a:osgeo:mapserver:5.6.8
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cpe:2.3:a:osgeo:mapserver:5.6.9
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cpe:2.3:a:osgeo:mapserver:6.0.0
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cpe:2.3:a:osgeo:mapserver:6.0.1
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cpe:2.3:a:osgeo:mapserver:6.0.2
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cpe:2.3:a:osgeo:mapserver:6.0.3
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cpe:2.3:a:osgeo:mapserver:6.0.4
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cpe:2.3:a:osgeo:mapserver:6.0.5
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cpe:2.3:a:osgeo:mapserver:6.0.6
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cpe:2.3:a:osgeo:mapserver:6.2.0
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cpe:2.3:a:osgeo:mapserver:6.2.1
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cpe:2.3:a:osgeo:mapserver:6.2.2
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cpe:2.3:a:osgeo:mapserver:6.2.3
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cpe:2.3:a:osgeo:mapserver:6.2.4
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cpe:2.3:a:osgeo:mapserver:6.4.0
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cpe:2.3:a:osgeo:mapserver:6.4.1
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cpe:2.3:a:osgeo:mapserver:6.4.2
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cpe:2.3:a:osgeo:mapserver:6.4.3
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cpe:2.3:a:osgeo:mapserver:6.4.4
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cpe:2.3:a:osgeo:mapserver:6.4.5
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cpe:2.3:a:osgeo:mapserver:6.4.6
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cpe:2.3:a:osgeo:mapserver:7.0.0
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cpe:2.3:a:osgeo:mapserver:7.0.1
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cpe:2.3:a:osgeo:mapserver:7.0.2
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cpe:2.3:a:osgeo:mapserver:7.0.3
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cpe:2.3:a:osgeo:mapserver:7.0.4
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cpe:2.3:a:osgeo:mapserver:7.0.5
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cpe:2.3:a:osgeo:mapserver:7.0.6
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cpe:2.3:a:osgeo:mapserver:7.0.7
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cpe:2.3:a:osgeo:mapserver:7.0.8
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cpe:2.3:a:osgeo:mapserver:7.1.0
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cpe:2.3:a:osgeo:mapserver:7.2.0
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cpe:2.3:a:osgeo:mapserver:7.2.1
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cpe:2.3:a:osgeo:mapserver:7.2.2
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cpe:2.3:a:osgeo:mapserver:7.2.3
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cpe:2.3:a:osgeo:mapserver:7.3.0
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cpe:2.3:a:osgeo:mapserver:7.4.0
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cpe:2.3:a:osgeo:mapserver:7.4.1
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cpe:2.3:a:osgeo:mapserver:7.4.2
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cpe:2.3:a:osgeo:mapserver:7.4.3
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cpe:2.3:a:osgeo:mapserver:7.4.4
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cpe:2.3:a:osgeo:mapserver:7.4.5
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cpe:2.3:a:osgeo:mapserver:7.5.0
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cpe:2.3:a:osgeo:mapserver:7.6.0
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cpe:2.3:a:osgeo:mapserver:7.6.1
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cpe:2.3:a:osgeo:mapserver:7.6.2
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cpe:2.3:a:osgeo:mapserver:7.6.3
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cpe:2.3:a:osgeo:mapserver:7.6.4
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cpe:2.3:a:osgeo:mapserver:7.6.5
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cpe:2.3:a:osgeo:mapserver:7.6.6
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cpe:2.3:a:osgeo:mapserver:7.6.7
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cpe:2.3:a:osgeo:mapserver:8.0.0
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cpe:2.3:a:osgeo:mapserver:8.0.1
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cpe:2.3:a:osgeo:mapserver:8.0.2
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cpe:2.3:a:osgeo:mapserver:8.2.0
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cpe:2.3:a:osgeo:mapserver:8.2.1
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cpe:2.3:a:osgeo:mapserver:8.2.2
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cpe:2.3:a:osgeo:mapserver:8.4.0
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cpe:2.3:a:osgeo:mapserver:8.4.1