CVE-2026-20256 | Improper Input Validation through Protocol-Relative URL in Classic Dashboards in Splunk Enterprise

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.

Published: 2026-06-10 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]

NVD Status：Analyzed，CVE State: published

View at NVD, CVE.org, EUVD

Threat Intelligence & Risk Assessment for CVE-2026-20256

EPSS CVSS CWE GHSA Affected

Conclusion & alert: CVE-2026-20256 is rated Low Risk (29/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.26%). Mandatory action: Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-20256

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.04%	0.26%	+0.21%
2	2026-06-11	—	0.04%	—

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-20256

CVSS metrics for this CVE.

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.7	3.1	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:H) Serious risk that confidential data gets exposed in a big way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:N) Service keeps running; no real outage angle.	2.1	3.6	[email protected]

Weakness enumeration for CVE-2026-20256

CWE-20 MITRE ↗

GitHub Security Advisory for CVE-2026-20256

GHSA-p326-4xf8-xp88 · Severity: medium — In Splunk Enterprise versions below 10.2.4, 10.0.7, 9.4.12, and 9.3.13, and Splunk Cloud Platform...

Affected software / configurations for CVE-2026-20256

Vendor	Product	Version	Raw CPE
splunk	splunk	>= 9.3.0, < 9.3.13	cpe:2.3:a:splunk:splunk:::::enterprise:::*
splunk	splunk	>= 9.4.0, < 9.4.12	cpe:2.3:a:splunk:splunk:::::enterprise:::*
splunk	splunk	>= 10.0.0, < 10.0.7	cpe:2.3:a:splunk:splunk:::::enterprise:::*
splunk	splunk	>= 10.2.0, < 10.2.4	cpe:2.3:a:splunk:splunk:::::enterprise:::*
splunk	splunk_cloud_platform	>= 9.3.2411, < 9.3.2411.132	cpe:2.3:a:splunk:splunk_cloud_platform::::::::
splunk	splunk_cloud_platform	>= 10.1.2507, < 10.1.2507.23	cpe:2.3:a:splunk:splunk_cloud_platform::::::::
splunk	splunk_cloud_platform	>= 10.2.2510, < 10.2.2510.15	cpe:2.3:a:splunk:splunk_cloud_platform::::::::
splunk	splunk_cloud_platform	>= 10.3.2512, < 10.3.2512.13	cpe:2.3:a:splunk:splunk_cloud_platform::::::::

References for CVE-2026-20256

URL	Tags
https://advisory.splunk.com/advisories/SVD-2026-0606	Vendor Advisory

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