CVE-2026-33721

Name: CVE-2026-33721
Creator: NVD / NIST
Published: 2026-03-27T01:16:19.67+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.86%

Last modified Jun 17, 2026

CVE-2026-33721 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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). EPSS estimates a 0.86% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

0.86%

54.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-787

Affected Software

Vendor	Product	Versions
Osgeo	Mapserver	>= 4.2.0, < 8.6.1

References

https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1Product, Release Notes
https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjpExploit, Mitigation, Vendor Advisory
https://lists.debian.org/debian-lts-announce/2026/04/msg00017.html

Timeline

Published: Mar 27, 2026
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2026-33721?

How severe is CVE-2026-33721?

CVE-2026-33721 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.86% probability of exploitation in the next 30 days.

How do I fix CVE-2026-33721?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-33721?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST