CVE-2026-33721: MapServer has heap buffer overflow in SLD `Categorize` Threshold parsing
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 SLDBODY). Version 8.6.1 patches the issue.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-33721?
CVE-2026-33721 is classified as a high severity vulnerability due to the potential for remote exploitation via heap buffer overflow.
How do I fix CVE-2026-33721?
To fix CVE-2026-33721, upgrade MapServer to version 8.6.1 or later, as this version addresses the heap buffer overflow issue.
Who is affected by CVE-2026-33721?
CVE-2026-33721 affects all versions of MapServer from 4.2 up to but not including 8.6.1.
What type of vulnerability is CVE-2026-33721?
CVE-2026-33721 is a heap buffer overflow vulnerability in the SLD parser of MapServer.
Can CVE-2026-33721 be exploited remotely?
Yes, CVE-2026-33721 can be exploited remotely by an unauthenticated attacker through malicious SLD inputs.