Mapserver · Mapserver · CVE-2026-45104
**Name of the Vulnerable Software and Affected Versions**
MapServer versions 6.4.0 through 8.6.2
**Description**
A NULL pointer dereference occurs when the `msSLDParseUserStyle` function calls ` SLDApplyRuleValues(psRule, psLayer, 1)` for any `<Rule>` containing an `<ElseFilter/>`. The system assumes `msSLDParseRule` added one class; however, if the rule lacks a symbolizer, `msSLDParseRule` adds zero classes, leading the system to index ` class[-1]`. This can be triggered without authentication using a well-formed 200-byte SLD via the 'SLD BODY=' parameter in the WMS endpoint.
**Recommendations**
Update to version 8.6.3.