MapServer up to 8.6.0 SLD out-of-bounds write

CVSS Meta Temp Score
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CTI Interest Score
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5.2$0-$5k1.34

Summaryinfo

A vulnerability was found in MapServer up to 8.6.0 and classified as critical. Impacted is an unknown function of the component SLD Handler. Such manipulation leads to out-of-bounds write. This vulnerability is listed as CVE-2026-33721. The attack may be performed from remote. There is no available exploit. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in MapServer up to 8.6.0. It has been rated as critical. Affected by this issue is an unknown code of the component SLD Handler. The manipulation with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is handled as CVE-2026-33721 since 03/23/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. The technical details are unknown and an exploit is not available.

The vulnerability scanner Nessus provides a plugin with the ID 304168 (Linux Distros Unpatched Vulnerability : CVE-2026-33721), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 8.6.1 eliminates this vulnerability. The upgrade is hosted for download at github.com.

The vulnerability is also documented in the vulnerability database at Tenable (304168). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Name

Version

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 5.3
VulDB Meta Temp Score: 5.2

VulDB Base Score: 5.3
VulDB Temp Score: 5.1
VulDB Vector: 🔒
VulDB Reliability: 🔍

CNA Base Score: 5.3
CNA Vector (GitHub_M): 🔒

CVSSv2info

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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Out-of-bounds write
CWE: CWE-787 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 304168
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-33721

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: MapServer 8.6.1

Timelineinfo

03/23/2026 CVE reserved
03/27/2026 +4 days Advisory disclosed
03/27/2026 +0 days VulDB entry created
03/30/2026 +2 days VulDB entry last update

Sourcesinfo

Product: github.com

Advisory: GHSA-cv4m-mr84-fgjp
Status: Confirmed

CVE: CVE-2026-33721 (🔒)
GCVE (CVE): GCVE-0-2026-33721
GCVE (VulDB): GCVE-100-353798

Entryinfo

Created: 03/27/2026 07:03
Updated: 03/30/2026 01:31
Changes: 03/27/2026 07:03 (65), 03/30/2026 01:31 (2)
Complete: 🔍
Cache ID: 216:672:103

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