A flaw in the Firecracker jailer component allows a locally privileged user who can write to the jailer’s pre‑created directories to exploit a symbolic‑link following defect during startup initialization. The user can create a symlink that points to any host file, and when the jailer runs with root privileges it copies files through that link, resulting in the unintended overwriting of arbitrary files on the host. This code path is a classic example of CWE‑61, where insufficient validation of file paths leads to unauthorized file manipulation.

The vulnerability affects Amazon Firecracker containers running Linux, specifically versions released as v1.13.1 and earlier and the 1.14.0 release. The issue is confined to the jailer component responsible for preparing isolated environments for microVMs on a host system.

The CVSS v3.1 score of 6.0 indicates a moderate impact. EPSS indicates the exploitation probability is below 1%, and the vulnerability has not been catalogued in the CISA KEV list. The exploit requires local access to a user account with write permissions to the jailer directories and the ability to start the jailer process with elevated privileges. Without these conditions the vulnerability is not exploitable, so the attack vector is largely confined to systems where the host user can control the jailer environment.