Improper input validation in Splunk
CVE-2026-20256
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.
Vulnerability class: Drupalgeddon 2 (CVE-2018-7600)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.7 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N.
EPSS exploit prediction
EPSS: 0.004 (27.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 27th percentile — 27.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000
Affected products
- Splunk
- Splunk Cloud Platform — versions 10.3.2512, 10.2.2510, 10.1.2507
- Splunk Cloud Platform
- Splunk Enterprise — versions 10.2, 10.0, 9.4
Weakness classification (CWE)
References
- advisory.splunk.com/advisories/SVD-2026-0606 (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-20256?
- CVE-2026-20256 is a medium-severity vulnerability in Splunk, classified under Improper Input Validation. CVSS score: 5.7/10. Published 2026-06-10.
- How severe is CVE-2026-20256?
- Medium severity. CVSS v3 base score is 5.7 out of 10.