CVE-2026-45104

Name: CVE-2026-45104
Creator: NVD / NIST
Published: 2026-05-27T20:16:38.407+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 0.32%

Last modified Jun 17, 2026

CVE-2026-45104 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 0.32% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Probability

0.32%

23.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Osgeo	Mapserver	>= 6.4.0, < 8.6.3

References

https://github.com/MapServer/MapServer/security/advisories/GHSA-4h8g-378q-r75mExploit, Mitigation, Vendor Advisory

Timeline

Published: May 27, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-45104?

How severe is CVE-2026-45104?

CVE-2026-45104 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.32% probability of exploitation in the next 30 days.

How do I fix CVE-2026-45104?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-45104?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST