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Unlock with Pro - from £29/user/moDetect LaunchServer FileServerHandler Unauthenticated Path Traversal (CVE-2026-54617) in Google Chronicle
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
YARA-L Detection Query
rule launchserver_fileserverhandler_path_traversal {
meta:
author = "detection-engineering"
description = "Detects path traversal attempts against LaunchServer FileServerHandler (CVE-2026-54617)"
severity = "CRITICAL"
events:
$e.metadata.event_type = "NETWORK_HTTP"
$e.target.url = /FileServerHandler/ nocase
re.regex($e.target.url, `(\.\.%2f|\.\.%5c|\.\.\/|%2e%2e%2f|\.\.%c0%af)`)
condition:
$e
}Chronicle YARA-L rule detecting HTTP requests to the LaunchServer FileServerHandler endpoint containing path traversal sequences.
Data Sources
Required Tables
False Positives & Tuning
- Authorized vulnerability scanning traffic
- Legitimate encoded characters in launcher asset requests
- Proxy logging of pre-normalized URLs
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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