CVE-2026-33721
MapServer has heap buffer overflow in SLD `Categorize` Threshold parsing
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.
INFO
Published Date :
March 27, 2026, 1:16 a.m.
Last Modified :
April 17, 2026, 6:16 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | HIGH | [email protected] |
Solution
- Update MapServer to version 8.6.1 or later.
- Apply patches provided by the vendor.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-33721.
| URL | Resource |
|---|---|
| https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1 | Product Release Notes |
| https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp | Exploit Mitigation Vendor Advisory |
| https://lists.debian.org/debian-lts-announce/2026/04/msg00017.html |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-33721 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-33721
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-33721 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-33721 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
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CVE Modified by af854a3a-2127-422b-91ae-364da2661108
Apr. 17, 2026
Action Type Old Value New Value Added Reference https://lists.debian.org/debian-lts-announce/2026/04/msg00017.html -
Initial Analysis by [email protected]
Apr. 01, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:osgeo:mapserver:*:*:*:*:*:*:*:* versions from (including) 4.2.0 up to (excluding) 8.6.1 Added Reference Type GitHub, Inc.: https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp Types: Exploit, Mitigation, Vendor Advisory -
New CVE Received by [email protected]
Mar. 27, 2026
Action Type Old Value New Value Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Added CWE CWE-787 Added Reference https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1 Added Reference https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp