Detect CVE-2026-20253: Splunk Enterprise Missing Authentication for Critical Function in Elastic Security
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
Elastic Detection Query
sequence by source.ip with maxspan=5m
[network where network.application == "http" and
url.path : ("/services/search/jobs", "/services/data/inputs*", "/services/admin*", "/services/authentication*", "/en-US/splunkd/__raw/services*") and
not (http.request.headers.authorization : "*" or http.request.headers.cookie : "*splunkd_*") and
http.request.method in ("POST", "GET", "DELETE", "PUT")]
[network where network.application == "http" and
url.path : ("/services/search/jobs*", "/services/data*") and
http.response.status_code in (200, 201, 400, 500)]EQL sequence detection correlating unauthenticated requests to Splunk critical API endpoints followed by server responses, indicating potential exploitation of missing authentication controls.
Data Sources
Required Tables
False Positives & Tuning
- Internal network probes or health checkers not sending authentication headers
- Splunk SDK clients with misconfigured authentication settings
- Network devices with SSL inspection stripping authentication headers before logging
- Development or test environments with authentication intentionally disabled
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
Unlock Pro Content
Get the full detection package for CVE-2026-20253 including response playbook, investigation guide, and atomic red team tests.