CVE-2026-20256: Splunk

Medium severity, CVSS 5.7. EPSS: 0.4% chance of exploitation in the next 30 days.

In Splunk Enterprise versions below 10.2.4, 10.0.7, 9.4.12, and 9.3.13, and Splunk Cloud Platform versions below 10.3.2512.13, 10.2.2510.15, 10.1.2507.23, and 9.3.2411.132, a low-privileged user that does not hold the 'admin' or 'power' Splunk roles could cause data exfiltration through classic dashboards by redirecting a victim to an external site using a protocol-relative URL in a drill-down link.<br><br>The vulnerability exists because the URL classifier in classic dashboards only recognizes `http://` and `https://` schemes when checking for external URLs. Protocol-relative URLs such as `//attacker.com` bypass this check entirely, and Splunk Web does not show the external-navigation warning dialog to the victim.

Affected products

• Splunk Splunk: from 9.3.0, before 9.3.13 (fixed in 9.3.13); from 9.4.0, before 9.4.12 (fixed in 9.4.12); from 10.0.0, before 10.0.7 (fixed in 10.0.7); from 10.2.0, before 10.2.4 (fixed in 10.2.4)
• Splunk Splunk Cloud Platform: from 9.3.2411, before 9.3.2411.132 (fixed in 9.3.2411.132); from 10.1.2507, before 10.1.2507.23 (fixed in 10.1.2507.23); from 10.2.2510, before 10.2.2510.15 (fixed in 10.2.2510.15); from 10.3.2512, before 10.3.2512.13 (fixed in 10.3.2512.13)

Published 2026-06-10. Last modified 2026-06-17.