Detect CVE-2026-20253: Splunk Enterprise Missing Authentication for Critical Function in CrowdStrike LogScale
Detects exploitation attempts targeting CVE-2026-20253, a missing authentication vulnerability (CWE-306) in Splunk Enterprise. This KEV-listed vulnerability allows unauthenticated access to critical Splunk functions. Attackers may leverage this to execute searches, exfiltrate data, or manipulate Splunk configurations without valid credentials.
MITRE ATT&CK
- Tactic
- Initial Access Persistence Collection
LogScale Detection Query
#event_simpleName=NetworkConnectIP4
| DestinationPort in (8000, 8089, 9997, 8088)
| HttpUrl = "/services/search/jobs*" OR HttpUrl = "/services/data/inputs*" OR HttpUrl = "/services/admin*" OR HttpUrl = "/services/authentication*" OR HttpUrl = "/en-US/splunkd/__raw/services*"
| NOT (HttpRequestHeaders = "*Authorization: Splunk*" OR HttpRequestHeaders = "*Authorization: Bearer*" OR HttpCookieHeader = "*splunkd_*")
| HttpMethod in ("POST", "GET", "DELETE", "PUT")
| stats count() as request_count, values(HttpUrl) as accessed_paths, values(HttpMethod) as methods by RemoteAddressIP4, LocalAddressIP4, DestinationPort
| where request_count > 1
| sort -request_countCrowdStrike CQL query correlating network connection events to Splunk ports with unauthenticated HTTP requests to critical API paths, identifying potential exploitation of CVE-2026-20253.
Data Sources
Required Tables
False Positives & Tuning
- Falcon sensor on Splunk hosts may generate noise from internal Splunk process communications
- Authorized red team or penetration testing activities targeting Splunk infrastructure
- Splunk cluster peer-to-peer communications appearing as unauthenticated in some views
- Third-party SIEM integrations polling Splunk via legacy API patterns without modern auth
Other platforms for CVE-2026-20253
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Unauthenticated Splunk Search Job Creation via REST API
Expected signal: HTTP POST to port 8089 without Authorization header; Splunk web_access.log entry with null/anonymous user; network flow record to TCP/8089
- Test 2Unauthenticated Splunk User Enumeration via REST API
Expected signal: HTTP GET to /services/authentication/users on port 8089 without credentials; response body containing user list if vulnerable
- Test 3Unauthenticated Splunk Index Listing and Data Access
Expected signal: Sequential unauthenticated GET and POST requests to Splunk REST API; multiple different /services/ paths accessed from same source IP within short timeframe
- Test 4Unauthenticated Splunk Configuration Modification Attempt
Expected signal: HTTP POST to /services/data/inputs/ without Authorization header; Splunk audit log entry for configuration change with anonymous user context
References (4)
- https://advisory.splunk.com/advisories/SVD-2026-0603
- https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk
- https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk
- https://nvd.nist.gov/vuln/detail/CVE-2026-20253
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