Is CVE-2026-33721 actively exploited?

CVE-2026-33721 has no public evidence of in-the-wild exploitation as of 2026-04-17.

What is the CVSS score for CVE-2026-33721?

CVE-2026-33721 has a CVSS score of 5.3 (MEDIUM severity). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.

How do I patch CVE-2026-33721?

Patch guidance is available from osgeo security advisories. CVEDatabase generates AI-assisted remediation guidance on demand for CVE-2026-33721.

CVE-2026-33721 - remediation guidance & executive summary

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.

CVSS Metrics

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack Vector: network
Complexity: low
Privileges: none
User Action: none
Scope: unchanged
Confidentiality: none
Integrity: none
Availability: low
Weaknesses: CWE-787 · Out-of-bounds Write

Metadata

Primary Vendor: OSGEO
Published: 3/27/2026
Last Modified: 4/17/2026
Source: NIST NVD
Note: Verify all details with official vendor sources before applying patches.

CVE-2026-33721

Description

CVSS Metrics

Metadata

Affected Products

Remediation Guidance

Executive Summary