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Unlock with Pro - from £29/user/moDetect Flyto2 Core Arbitrary File Write via image.download Path Traversal (CVE-2026-67429) in Elastic Security
Detects exploitation of CVE-2026-67429, a critical (CVSS 10.0) arbitrary file write vulnerability in Flyto2 Core (pip package flyto-core) versions prior to 2.26.7. The image.download module and other file-writing modules fail to sanitize user-supplied filenames/paths (CWE-22 path traversal, CWE-73 external control of file name or path), allowing an unauthenticated or low-privileged attacker to write arbitrary files anywhere on the filesystem reachable by the flyto-core process. This can be leveraged to overwrite application code, cron files, SSH authorized_keys, systemd unit files, or web-accessible directories to achieve remote code execution. Detection focuses on identifying path traversal sequences and absolute/unexpected path targets passed to flyto-core's image.download and related file-writing endpoints, as well as downstream evidence such as newly written files in sensitive directories immediately following flyto-core process activity.
MITRE ATT&CK
- Tactic
- Initial Access Execution Persistence
Elastic Detection Query
sequence by host.name with maxspan=5m
[process where event.type == "start" and
(process.name : "python*" or process.name : "gunicorn" or process.name : "uwsgi") and
process.command_line : ("*flyto*", "*image.download*") and
process.command_line : ("*../*", "*..\\*", "*%2e%2e%2f*", "*%2e%2e/*")]
[file where event.type in ("creation", "change") and
(file.path : "/etc/*" or file.path : "/root/.ssh/*" or file.path : "*authorized_keys*" or file.path : "*cron.d*" or file.path : "C:\\Windows\\*" or file.path : "*wwwroot*" or file.path : "*inetpub*")]Elastic EQL sequence detecting a flyto-core process invoked with path traversal sequences targeting image.download followed by a file write to a sensitive filesystem path, indicating CVE-2026-67429 exploitation.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate penetration testing activity against the flyto-core service in a non-production environment
- Unrelated administrative scripts that coincidentally write to monitored sensitive paths within the sequence window
- Misconfigured monitoring agents generating synthetic file events near flyto-core process starts
Other platforms for CVE-2026-67429
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 1Path Traversal via image.download to /etc/
Expected signal: Process event for the python3 process with command line referencing flyto_core and a path containing multiple '../' sequences; file creation event for /etc/flyto_poc_test.txt.
- Test 2Arbitrary File Write to SSH authorized_keys
Expected signal: File modification event on /root/.ssh/authorized_keys initiated by the flyto-core python process shortly after a traversal-pattern process command line.
- Test 3Path Traversal via image.download on Windows
Expected signal: Process creation event for python.exe with command line containing flyto and backslash traversal sequences; file creation event under C:\Windows\Temp\.
References (5)
- https://github.com/flytohub/flyto-core/security/advisories/GHSA-2956-977x-2w3r
- https://nvd.nist.gov/vuln/detail/CVE-2026-67429
- https://github.com/flytohub/flyto-core/commit/d5f89d71303e3c1e6418d347c5c55fcd173cc8cc
- https://github.com/flytohub/flyto-core/releases/tag/v2.26.6
- https://github.com/advisories/GHSA-2956-977x-2w3r
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