# 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.

- **Severity:** Medium 5.7 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N`)
- **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 available:** No
- **Published:** 10 Jun 2026
- **Updated:** 10 Jun 2026
- **Also known as:** GHSA-73fj-f5qc-x4jf

## 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 (Improper Input Validation)

## Which versions are affected by CVE-2026-20257?

It affects 2 products.


Products: 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.

## 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](https://insights.sbomify.com/CVE-2026-20253/): Splunk Enterprise Missing Authentication for Critical Function (critical 9.8, exploited in the wild)
- [CVE-2026-76268](https://insights.sbomify.com/CVE-2026-76268/): Missing Authentication for Critical Function in the Patroni REST API in Splunk Enterprise (critical 9.8)
- [CVE-2026-76284](https://insights.sbomify.com/CVE-2026-76284/): Improper Neutralization in Splunk Enterprise (critical 9.8)
- [CVE-2026-76285](https://insights.sbomify.com/CVE-2026-76285/): Improper Adherence to Coding Standards in Splunk Enterprise (critical 9.8)
- [CVE-2017-17067](https://insights.sbomify.com/CVE-2017-17067/): Auth bypass in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-20257 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-20257 in the wild and no public exploit code.

Affected product: Splunk Splunk. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-20257/ (Markdown: https://insights.sbomify.com/CVE-2026-20257/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-20257
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-20257
- OSV: https://osv.dev/vulnerability/CVE-2026-20257

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-20257/
Summaries are generated and may contain mistakes; the official description above is the record.