CVE-2026-20256 Improper Input Validation through Protocol-Relative URL in Classic Dashboards in Splunk Enterprise
Low-privileged users can exfiltrate data by redirecting victims to external sites via protocol-relative URLs in Splunk dashboards, bypassing security warnings.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-20256?
CVE-2026-20256 is a medium-severity vulnerability in Splunk Splunk, published on 10 Jun 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
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.
Weakness: CWE-20
Which versions are affected by CVE-2026-20256?
It affects 2 products.
Products include Splunk Splunk, Splunk Splunk Cloud Platform.
How do I fix CVE-2026-20256?
No fix has been published for CVE-2026-20256 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-20256 being exploited?
There is no known exploitation of CVE-2026-20256 in the wild and no public exploit code.
Other vulnerabilities in Splunk Splunk
- CVE-2026-20253 Splunk Enterprise Missing Authentication for Critical Function
- CVE-2026-76268 Missing Authentication for Critical Function in the Patroni REST API in Splunk Enterprise
- CVE-2026-76284 Improper Neutralization in Splunk Enterprise
- CVE-2026-76285 Improper Adherence to Coding Standards in Splunk Enterprise
- CVE-2017-17067 Auth bypass in n/a
Sources
Also known as GHSA-p326-4xf8-xp88.