Out-of-bounds write in MapServer - CVE-2026-33721
Published: April 20, 2026
Vulnerability identifier: #VU126491
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-33721
CWE-ID: CWE-787
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to out-of-bounds write in msSLDParseRasterSymbolizer when parsing a crafted SLD ColorMap/Categorize structure with more than 100 Threshold elements. A remote attacker can send a specially crafted SLD request to cause a denial of service.
The issue is commonly reachable via WMS GetMap with SLD_BODY, depending on deployment configuration.
Affected software
MapServer
Fedora
mapserver
Fedora
mapserver
How to mitigate CVE-2026-33721
Install security update from vendor's website.
MapServer - update to 8.6.1
mapserver - addressed in versions 8.4.1-3.fc42, 8.4.1-3.fc43, 8.6.1-1.el9, 8.6.1-1.fc44
mapserver - addressed in versions 8.4.1-3.fc42, 8.4.1-3.fc43, 8.6.1-1.el9, 8.6.1-1.fc44