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Splunk Enterprise CVE-2026-20257

| EUVDEUVD-2026-36085 MEDIUM
Improper Input Validation (CWE-20)
2026-06-10 cisco GHSA-73fj-f5qc-x4jf
5.7
CVSS 3.1 · NVD
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Severity by source

NVD PRIMARY
5.7 MEDIUM
AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N
vuln.today AI
5.7 MEDIUM

Network-accessible dashboard feature exploited by authenticated low-privilege user; victim interaction mandatory; only browser-side confidentiality impacted with no integrity or availability effect.

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

Primary rating from NVD.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

2
Analysis Generated
Jun 10, 2026 - 20:36 vuln.today
Patch available
Jun 10, 2026 - 20:01 EUVD

DescriptionNVD

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 craft a classic dashboard that exfiltrates sensitive data from the browser of a higher-privileged user who views it.

The exfiltration is possible because classic dashboard panels do not fully validate style attribute values, which can allow for requests to reach external domains outside the configured Trusted Domains List.

The vulnerability requires the attacker to phish the victim by tricking them into initiating a request within their browser. The low-privileged user should not be able to exploit the vulnerability at will.

AnalysisAI

Classic dashboard style attribute injection in Splunk Enterprise and Splunk Cloud Platform enables a low-privileged authenticated user to craft panels that bypass the Trusted Domains List and exfiltrate sensitive data from a higher-privileged user's browser session. Affected branches span Splunk Enterprise below 10.2.4, 10.0.7, 9.4.12, and 9.3.13, and multiple Splunk Cloud Platform release trains. No public exploit has been identified at time of analysis, and SSVC rates current exploitation as none with partial technical impact, though the high confidentiality impact potential warrants prompt patching in environments where low-privileged users can share dashboards with administrators.

Technical ContextAI

The root cause is CWE-20 (Improper Input Validation) within Splunk's classic dashboard rendering engine. Specifically, classic dashboard panel definitions accept CSS style attribute values that are not fully sanitized before being rendered in a viewer's browser. This allows injection of CSS constructs - such as background-image or similar properties - that reference arbitrary external URLs, effectively circumventing the Trusted Domains List enforcement intended to restrict outbound browser requests. When a higher-privileged user loads the malicious dashboard, their browser issues HTTP requests to attacker-controlled infrastructure, potentially leaking HTTP headers including session tokens. CPE strings cpe:2.3:a:splunk:splunk_enterprise and cpe:2.3:a:splunk:splunk_cloud_platform confirm both the self-hosted and managed SaaS products are affected across multiple release branches. This is a well-understood class of CSS-based data exfiltration, distinct from traditional reflected or stored XSS in that it operates via style injection rather than script execution.

RemediationAI

Upgrade Splunk Enterprise to version 10.2.4, 10.0.7, 9.4.12, or 9.3.13 (or later within the respective branch) as confirmed by the vendor advisory SVD-2026-0607 at https://advisory.splunk.com/advisories/SVD-2026-0607. Splunk Cloud Platform customers should verify their instance has been updated to 10.3.2512.13, 10.2.2510.15, 10.1.2507.23, or 9.3.2411.132 depending on their deployed release train; Splunk Cloud Platform updates are typically managed by Splunk and may already be applied. As a compensating control prior to patching, restrict classic dashboard creation and sharing permissions to trusted users only by reviewing role-based access controls - note this may impact legitimate analyst workflows. Additionally, audit existing classic dashboards for unexpected external domain references in style attributes, and ensure the Trusted Domains List is configured as restrictively as operationally possible to limit the blast radius of any bypass. Blocking outbound HTTP/HTTPS traffic from Splunk web servers to non-approved external domains at the network perimeter can further reduce exfiltration risk but may disrupt legitimate integrations.

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CVE-2026-20257 vulnerability details – vuln.today

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