Kestra's inputFiles task writes rendered file names directly to the task working directory. Prior to specific releases, the task does not sanitize or normalize path segments. An attacker that can supply untrusted execution or webhook data into an inputFiles filename can include '../' sequences, allowing them to create or overwrite files outside the intended directory.

The vulnerability affects Kestra versions 1.3.18 and earlier, 1.2.18 and earlier, 1.1.18 and earlier, and 1.0.42 and earlier. The patch is available in releases 1.3.19, 1.2.19, 1.1.19, and 1.0.43.

The CVSS score is 6.5, indicating a medium severity. EPSS is not available and the vulnerability is not listed in CISA's KEV catalog. It is inferred that exploitation requires the ability to create or modify flows or webhook data that reach the Kestra instance, giving an attacker the ability to write arbitrary files on the worker filesystem. This could lead to configuration tampering, privilege escalation, or data exfiltration in a multi‑tenant deployment.