Splunk released three security advisories on May 20, 2026, addressing critical vulnerabilities across Splunk Enterprise, Splunk Cloud Platform, and the Splunk AI Toolkit app.
Tracked as CVE-2026-20238, CVE-2026-20239, and CVE-2026-20240, the flaws allow low-privileged attackers to trigger denial-of-service conditions, leak session cookies, and bypass role-based access controls, all without requiring administrative credentials.
Splunk Patched Multiple Flaws
The most disruptive CVE-2026-20240 flaw resides in the splunk_archiver app’s coldToFrozen.sh script, which accepts arbitrary file paths without restricting operations to safe directories.
A low-privileged user without ‘admin’ or ‘power’ roles can exploit this missing input validation (CWE-20) to rename critical Splunk directories, rendering the instance completely non-functional.
The attack vector is network-accessible and requires no user interaction, making it an attractive target for insider threats or compromised low-privilege accounts.
Affected versions span the widest range of any flaw in this batch:
| Product | Affected Versions | Fixed Version |
|---|---|---|
| Splunk Enterprise 10.2 | 10.2.0 – 10.2.1 | 10.2.2 |
| Splunk Enterprise 10.0 | 10.0.0 – 10.0.4 | 10.0.5 |
| Splunk Enterprise 9.4 | 9.4.0 – 9.4.10 | 9.4.11 |
| Splunk Enterprise 9.3 | 9.3.0 – 9.3.11 | 9.3.12 |
| Splunk Cloud Platform 9.3.2411 | Below 9.3.2411.129 | 9.3.2411.129 |
As an immediate workaround, Splunk advises turning off the Splunk Archiver app, which will halt automated cold-to-frozen bucket transitions. The vulnerability was discovered and reported by external researcher Alex Hordijk (hordalex).
A high-severity information disclosure flaw (CVE-2026-20239, CWE-532) in Splunk Enterprise affects versions below 10.2.2 and 10.0.5, as well as multiple Splunk Cloud Platform branches below 10.3.2512.8, 10.2.2510.11, 10.1.2507.21, and 10.0.2503.13.
The vulnerability is rooted in the TcpChannel component’s failure to sanitize output buffers before writing to logs, logging complete I/O buffer contents, including session cookies and full HTTP response bodies, at WARN level during socket errors.
Any authenticated user with access to the _internal index can read these logs and extract live session credentials.
This mirrors a pattern Splunk has encountered across multiple advisory cycles, with earlier _internal index disclosure bugs patched in February and March 2026.
Splunk recommends immediately restricting _internal index access to administrator-level roles pending patch deployment, and is actively monitoring and patching Splunk Cloud Platform instances. Charlie Huggard of Splunk identified the flaw.
A logic flaw in CVE-2026-20238, how the Splunk AI Toolkit handles inherited search filters, allows low-privileged users to access data they should be restricted from viewing.
The app ships an authorize.conf file containing a srchFilter entry that modifies the built-in ‘user’ role.
Because Splunk combines inherited search filters using the OR SPL operator, this injected filter silently overrides more restrictive srchFilter configurations applied to child roles, effectively nullifying data segmentation controls.
Versions below 5.7.3 are affected. Administrators who cannot patch immediately can either remove the offending srchFilter line from the default authorize.conf or override it with an empty value in a local configuration file.
Both workarounds make the ai_agent_run_history_index searchable by all users, requiring supplementary role-level index access restrictions via the srchIndexesAllowed setting. Martin Müller of Splunk reported the flaw.
Patch and Mitigation
Given that all three CVEs require only low-level authenticated access with no user interaction, organizations running internal Splunk deployments with broad user bases face elevated risk until patches are applied. Recommended immediate actions:
- Splunk Enterprise: Upgrade to 10.2.2, 10.0.5, 9.4.11, or 9.3.12 depending on your version branch
- Splunk Cloud Platform: Splunk is actively patching managed instances; verify version status via the advisory portal
- Splunk AI Toolkit: Upgrade to version 5.7.3 or higher
- Interim controls: Disable Splunk Archiver app, restrict
_internalindex access to admin roles, and auditauthorize.conffiles for roguesrchFilterentries
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