Mapserver: From 6.4.0 to before 8.6.3, msSLDParseUserStyle always calls _SLDApplyRuleValues(psRule, psLayer, 1); for any <Rule> carrying <ElseFilter/> — it… (CVE-2026-45104)
Description
MapServer versions from 6.4.0 up to but not including 8.6.3 contain a vulnerability where processing a specific SLD (Styled Layer Descriptor) with an <ElseFilter/> element can cause a NULL pointer dereference. This occurs because the function msSLDParseUserStyle incorrectly assumes a class is added when it may not be, leading to an out-of-bounds index. A crafted 200-byte SLD via the WMS SLD_BODY parameter can trigger this without authentication. The issue is fixed in version 8.6.3.
CVSS v3.1
Score 7.5high
Affected software
pkg:deb/ubuntu/mapserver?arch=source&distro=xenialpkg:deb/ubuntu/mapserver?arch=source&distro=bionicpkg:deb/ubuntu/mapserver?arch=source&distro=focalpkg:deb/ubuntu/mapserver?arch=source&distro=jammypkg:deb/ubuntu/mapserver?arch=source&distro=noblepkg:deb/ubuntu/mapserver?arch=source&distro=questingpkg:deb/ubuntu/mapserver?arch=source&distro=stonkingpkg:deb/ubuntu/mapserver?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
MapServer, a web-based GIS application system, has a vulnerability in versions 6.4.0 through before 8.6.3 where the function msSLDParseUserStyle calls _SLDApplyRuleValues with an invalid index when processing an SLD <Rule> containing <ElseFilter/> without a symbolizer. This leads to a NULL pointer dereference due to indexing _class[-1]. The vulnerability can be triggered remotely without authentication by sending a well-formed 200-byte SLD via the WMS SLD_BODY parameter. The flaw is resolved in version 8.6.3.
Potential Impact
The vulnerability causes a NULL pointer dereference resulting in a denial of service (application crash) with no confidentiality, integrity, or authentication impact. It can be triggered remotely without authentication by sending a crafted SLD payload to the WMS service.
Mitigation Recommendations
An official fix is available in MapServer version 8.6.3. Users should upgrade to version 8.6.3 or later to remediate this vulnerability. No other mitigation or workaround is indicated.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-45104
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:25.10","Ubuntu:26.10","Ubuntu:26.04:LTS"]
- Cvss Version
- 3.1
Threat ID: 6ad3f65b2cdf04f656665d52
Added to database: 10/17/2026, 22:27:39 UTC
Last enriched: 10/18/2026, 01:30:53 UTC
Last updated: 10/18/2026, 01:30:53 UTC
Views: 2
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