Vulnerability record · CVE-2026-33721 · published 27 March 2026

CVE-2026-33721: Osgeo mapserver out-of-bounds write vulnerability

Osgeo · Mapserver

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.

7.5 CVSS 3.1 High EPSS 0.82% · top 44.6% CWE-787 · Out-of-bounds write

7.5CVSS 3.1 base score

0.82%EPSS exploitation probability, 30 days

NoNot in CISA KEV

1Affected product versions listed by NVD

3References, 1 tagged exploit

17 Jun 2026Last modified by NVD

Description

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

Mapserver Osgeo

References

Link	Tags
https://github.com/MapServer/MapServer/releases/tag/rel-8-6-1	ProductRelease Notes
https://github.com/MapServer/MapServer/security/advisories/GHSA-cv4m-mr84-fgjp	ExploitMitigationVendor Advisory
https://lists.debian.org/debian-lts-announce/2026/04/msg00017.html

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

10.0CVE-2010-2540Osgeo mapserver permissions and access controls vulnerabilitymapserv.c in mapserv in MapServer before 4.10.6 and 5.x before 5.6.4 does not properly restrict the use of CGI command-line arguments that were inten…EPSS 3.8%2 Aug 2010 10.0CVE-2009-2281Osgeo mapserver memory buffer overflow vulnerabilityMultiple heap-based buffer underflows in the readPostBody function in cgiutil.c in mapserv in MapServer 4.x through 4.10.4 and 5.x before 5.4.2 allow…EPSS 5.9%23 Oct 2009 10.0CVE-2009-0839Osgeo mapserver memory buffer overflow vulnerabilityStack-based buffer overflow in mapserv.c in mapserv in MapServer 4.x before 4.10.4 and 5.x before 5.2.2, when the server has a map with a long IMAGEP…EPSS 9.0%31 Mar 2009 10.0CVE-2009-0840Osgeo mapserver memory buffer overflow vulnerabilityHeap-based buffer underflow in the readPostBody function in cgiutil.c in mapserv in MapServer 4.x before 4.10.4 and 5.x before 5.2.2 allows remote at…EPSS 5.3%31 Mar 2009 10.0CVE-2009-0841Osgeo mapserver path traversal vulnerabilityDirectory traversal vulnerability in mapserv.c in mapserv in MapServer 4.x before 4.10.4 and 5.x before 5.2.2, when running on Windows with Cygwin, a…EPSS 5.3%31 Mar 2009 10.0CVE-2009-1176Osgeo mapserver memory buffer overflow vulnerabilitymapserv.c in mapserv in MapServer 4.x before 4.10.4 and 5.x before 5.2.2 does not ensure that the string holding the id parameter ends in a '\0' char…EPSS 4.1%31 Mar 2009 10.0CVE-2009-1177Osgeo mapserver memory buffer overflow vulnerabilityMultiple stack-based buffer overflows in maptemplate.c in mapserv in MapServer 4.x before 4.10.4 and 5.x before 5.2.2 have unknown impact and remote …EPSS 2.9%31 Mar 2009 9.8CVE-2017-5522Debian linux memory buffer overflow vulnerabilityStack-based buffer overflow in MapServer before 6.0.6, 6.2.x before 6.2.4, 6.4.x before 6.4.5, and 7.0.x before 7.0.4 allows remote attackers to caus…EPSS 4.8%15 Mar 2017

Source: NIST National Vulnerability Database (record CVE-2026-33721), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.