Medium 5.3Published Mar 26, 2026

CVE-2026-33721MapServer has heap buffer overflow in SLD `Categorize` Threshold parsing

Updated under an hour ago (Oct 27, 2026, 2:30 PM ET)

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No exploitation reported and no EPSS estimate yet.

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Every CVE for MapServer

Exploited in the last 30 days

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.

CVSS: 5.3 MEDIUM (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Weakness (CWE): CWE-787
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: GitHub_M
NVD analysis: Modified
Record last updated: Apr 17, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

MapServer MapServer mapserver:mapserver (from the name)	from 4.2, < 8.6.1	CNA record
osgeo mapserver osgeo:mapserver	from 4.2.0 before 8.6.1	NVD

References

References

https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp	x-refsource-confirm, exploit, mitigation, vendor-advisory
https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1	x-refsource-misc, product, release-notes
https://lists.debian.org/debian-lts-announce/2026/04/msg00017.html

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.