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    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.

    Published:Mar 27, 2026
    Last Modified:Apr 17, 2026
    EPS:Mar 27, 2026
    EPSS Score:0.0021
    CVSS Score:5.3

    Affected Products

    Vendor
    Mapserver
    Product
    Mapserver
    Vendor
    Osgeo
    Product
    Mapserver

    Exploits

    https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp

    Common Weakness Enumeration

    CWE-787 Out-of-bounds Write

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High