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Unlock with Pro - from £29/user/moDetect LaunchServer FileServerHandler Unauthenticated Path Traversal (CVE-2026-54617) in Splunk
Detects exploitation attempts against pro.gravit.launcher:launchserver-api's FileServerHandler, which is vulnerable to an unauthenticated path traversal (CWE-22) allowing arbitrary file read (CWE-200) and disclosure of sensitive data such as credentials or keys (CWE-522) in versions <= 5.7.11. Attackers send crafted HTTP requests containing traversal sequences (../, encoded variants, absolute paths) to the LaunchServer file-serving endpoint to read files outside the intended web root, including server configs, private keys, and auth databases.
MITRE ATT&CK
- Tactic
- Initial Access Collection
SPL Detection Query
index=web_proxy OR index=iis (uri="*FileServerHandler*" OR url="*FileServerHandler*")
| regex uri="(\.\.%2f|\.\.%5c|\.\.\\\\|\.\.\/|%2e%2e%2f|%2e%2e\/|\.\.%c0%af)"
| stats count min(_time) as first_seen max(_time) as last_seen values(uri) as uris by src_ip, dest_ip, http_method
| where count > 0
| sort -countIdentifies path traversal attempts against the FileServerHandler endpoint in LaunchServer, associated with unauthenticated arbitrary file read exploitation.
Data Sources
Required Sourcetypes
False Positives & Tuning
- Automated vulnerability scanning tools performing authorized traversal checks
- Encoded characters in legitimate launcher mod/asset filenames
- Log ingestion misparsing of query strings
Other platforms for CVE-2026-54617
Testing Methodology
Validate this detection against 3 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 1Basic path traversal against FileServerHandler
Expected signal: Web/proxy access log entry showing GET request to FileServerHandler with '../' sequences and response body containing /etc/passwd content or a 200 status.
- Test 2URL-encoded traversal against FileServerHandler
Expected signal: Access log entry with percent-encoded traversal sequences in the request URI/query targeting FileServerHandler.
- Test 3Windows-style backslash traversal against FileServerHandler
Expected signal: IIS/web log entry showing a request to FileServerHandler containing '..%5c' sequences and an unusual response size for win.ini content.
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