CVE-2026-20257
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedIn 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThis is a stored Cross-Site Scripting (XSS) variant in Splunk Enterprise and Cloud Platform where classic dashboard panels fail to properly validate style attribute values. A low-privileged attacker can craft a malicious classic dashboard that, when viewed by a higher-privileged user with active session credentials, exfiltrates sensitive data to external domains outside the Trusted Domains List by leveraging the victim's browser to initiate requests.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data>= 9.3.0, < 9.3.13>= 9.4.0, < 9.4.12>= 10.0.0, < 10.0.7>= 10.2.0, < 10.2.4>= 9.3.2411, < 9.3.2411.132>= 10.1.2507, < 10.1.2507.23>= 10.2.2510, < 10.2.2510.15>= 10.3.2512, < 10.3.2512.13CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check Splunk Enterprise versionNavigate to Settings > About or run the command: splunk --version or access /en-US/account/info on the Splunk web interfaceAffected if The installed version falls within >= 9.3.0 and < 9.3.13, >= 9.4.0 and < 9.4.12, >= 10.0.0 and < 10.0.7, or >= 10.2.0 and < 10.2.4
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Check Splunk Cloud Platform versionNavigate to the Cloud Portal settings or check the version indicator in the Splunk Cloud web interfaceAffected if The installed version falls within >= 9.3.2411 and < 9.3.2411.132, >= 10.1.2507 and < 10.1.2507.23, >= 10.2.2510 and < 10.2.2510.15, or >= 10.3.2512 and < 10.3.2512.13
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Identify classic dashboard panels in useReview existing dashboards and locate panels that use the classic dashboard format (Simple XML-based dashboards) by checking the dashboard source or viewing dashboard propertiesAffected if Classic dashboard panels are present and accessible to low-privileged users who can modify panel style attributes
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Verify Trusted Domains List configurationNavigate to Settings > Server Settings > Trusted Domains or check the web.conf configuration file for the trustedDomain sslRejectCommonNames settingsAffected if The Trusted Domains List is empty, contains wildcard entries, or allows external domains that are not explicitly restricted, enabling data exfiltration to arbitrary external domains
Your environment is affected if you are running any Splunk version within the affected ranges AND have classic dashboard panels in use AND the Trusted Domains List permits outbound requests to external domains.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped9.3.139.3.2411.1329.4.12
Upgrade Splunk Enterprise to version 10.2.4+, 10.0.7+, 9.4.12+, or 9.3.13+ (or Cloud Platform to 10.3.2512.13+, 10.2.2510.15+, 10.1.2507.23+, or 9.3.2411.132+) and verify the Trusted Domains List configuration to restrict outbound requests.
Upgrade Splunk Enterprise to 9.3.13, 9.4.12, 10.0.7, or 10.2.4 (depending on current branch); upgrade Splunk Cloud Platform to 9.3.2411.132, 10.1.2507.23, 10.2.2510.15, or 10.3.2512.13
- Identify the currently installed Splunk Enterprise or Splunk Cloud Platform version using the Splunk UI (Settings > About) or by running: splunk version
- Determine which upgrade path applies based on your current version: 9.3.x -> upgrade to 9.3.13; 9.4.x -> upgrade to 9.4.12; 10.0.x -> upgrade to 10.0.7; 10.2.x -> upgrade to 10.2.4
- For Splunk Enterprise: Download the appropriate upgrade package from splunk.com and follow standard Splunk upgrade procedures (back up your configuration, stop Splunk, install new version, start Splunk)
- For Splunk Cloud Platform: Contact Splunk Support to schedule the upgrade to the fixed version (9.3.2411.132, 10.1.2507.23, 10.2.2510.15, or 10.3.2512.13)
- After upgrade, verify the version number matches the fixed release
- Test that classic dashboards function normally and that the style attribute validation now properly restricts external domain requests
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation4.0 h
- Implementation8.0 h
- Testing12.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-20257 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-20257 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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