Remote crash via unchecked Categorize threshold count
Published Mar 27, 2026 · Updated Mar 27, 2026
Heap-buffer overflow in MapServer 4.2 through 8.6.0 allows remote attackers to crash the service through a crafted SLD request. In msSLDParseRasterSymbolizer, the Categorize parser allocates 100 threshold pointers but checks nValues instead of nThresholds before appending, so extra Threshold elements write beyond the heap array. The crash requires a deployment that parses attacker-controlled SLD content, commonly through WMS GetMap when SLD_BODY is accepted.
Summary
What happened
Heap-buffer overflow in MapServer 4.2 through 8.6.0 allows remote attackers to crash the service through a crafted SLD request. In msSLDParseRasterSymbolizer, the Categorize parser allocates 100 threshold pointers but checks nValues instead of nThresholds before appending, so extra Threshold elements write beyond the heap array. The crash requires a deployment that parses attacker-controlled SLD content, commonly through WMS GetMap when SLD_BODY is accepted.
The record
- CVE
- CVE-2026-33721
- Published
- Mar 27, 2026
- Updated
- Mar 27, 2026
- Vendor
- MapServer
- Product
- MapServer
- Classifications
- CWE-787, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 27, 2026CVE publishedPublication date reported by the CVE source.
- Mar 27, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=>= 4.2, < 8.6.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
- MapServer SLD Categorize threshold proof of conceptproof of concept · validated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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