CVE-2026-20257 Improper Input Validation through Classic Dashboard CSS in Splunk Enterprise
Low-privileged users can exfiltrate sensitive data from higher-privileged users' browsers via crafted classic dashboards in Splunk Enterprise.
- 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-2026-20257?
CVE-2026-20257 is a medium-severity cross-site scripting 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 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.
Weakness: CWE-20
Which versions are affected by CVE-2026-20257?
It affects 2 products.
Products include Splunk Splunk, Splunk Splunk Cloud Platform.
How do I fix CVE-2026-20257?
No fix has been published for CVE-2026-20257 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-20257 being exploited?
There is no known exploitation of CVE-2026-20257 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-73fj-f5qc-x4jf.