CVE-2026-33721 | THREATINT

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.

PUBLISHED Reserved 2026-03-23 | Published 2026-03-27 | Updated 2026-04-17 | Assigner GitHub_M

MEDIUM: 5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

Problem types

CWE-787: Out-of-bounds Write

Product status

>= 4.2, < 8.6.1

affected

References

lists.debian.org/debian-lts-announce/2026/04/msg00017.html

github.com/...Server/security/advisories/GHSA-cv4m-mr84-fgjp

github.com/MapServer/MapServer/releases/tag/rel-8-6-1

cve.org (CVE-2026-33721)

nvd.nist.gov (CVE-2026-33721)

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