Vulnerability Description
MapServer is a system for developing web-based GIS applications. From 6.4.0 to before 8.6.3, msSLDParseUserStyle always calls _SLDApplyRuleValues(psRule, psLayer, 1); for any <Rule> carrying <ElseFilter/> — it assumes msSLDParseRule added one class. When the rule has no symbolizer (a structurally valid SLD), msSLDParseRule adds zero, and _SLDApplyRuleValues ends up indexing _class[-1], resulting in a NULL pointer dereference. A 200-byte well-formed SLD via the WMS SLD_BODY= parameter is enough to trigger this, no auth required. This vulnerability is fixed in 8.6.3.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Osgeo | Mapserver | >= 6.4.0, < 8.6.3 |
Related Weaknesses (CWE)
References
- https://github.com/MapServer/MapServer/security/advisories/GHSA-4h8g-378q-r75mExploitMitigationVendor Advisory
FAQ
What is CVE-2026-45104?
CVE-2026-45104 is a vulnerability with a CVSS score of 7.5 (HIGH). MapServer is a system for developing web-based GIS applications. From 6.4.0 to before 8.6.3, msSLDParseUserStyle always calls _SLDApplyRuleValues(psRule, psLayer, 1); for any <Rule> carrying <ElseFilt...
How severe is CVE-2026-45104?
CVE-2026-45104 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-45104?
Check the references section above for vendor advisories and patch information. Affected products include: Osgeo Mapserver.