CVE-2026-44881: Portainer: Arbitrary File Read via Git Symlink Injection in Stack Auto-Update

Synopsis

An arbitrary file read vulnerability exists in Portainer Community Edition, affecting versions 2.33.0 through before 2.33.8, 2.39.2, and 2.41.0. An authenticated user with stack management rights can create a Git-backed stack whose repository contains a symlink pointing to any file on the host filesystem; when Portainer reads the stack entry point, it follows the symlink and returns the target file's contents in the HTTP response. Successful exploitation gives the attacker read access to any file readable by the Portainer process, including secrets, credentials, and other sensitive host data. A patched-image rebuild at versions 2.33.8, 2.39.2, and 2.41.0 is available on HarborGuard for affected environments.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The Portainer API must be reachable over the network; an attacker sends HTTP requests to the /api/stacks and /api/stacks/{id}/file endpoints remotely.

• AuthenticationRequired

  A low-privilege account with rights to create or update a Git-backed stack is sufficient; no admin credentials are needed, and this permission is granted to users by default in Portainer CE.

• Victim interactionNot required

  No victim action is needed; the attacker triggers the file read entirely through their own API requests.

• Attack complexityDetail

  The exploit is reliable and condition-free: crafting a repository with a symlink entry and calling the stack file endpoint is deterministic with no race conditions or environmental dependencies.

Blast Radius

• Reads arbitrary files accessible to the Portainer process, including host secrets, TLS certificates, and environment variable files containing credentials.
• Reads Portainer's own internal configuration and authentication token stores, enabling credential harvesting for further lateral movement.
• Exposes Kubernetes kubeconfig files or Docker socket credentials stored on the host, which can be used to pivot into managed container environments.
• High impact on systems beyond the Portainer container itself (SC:H, SI:H, SA:H) means a successful read of the right credential file can grant an attacker control over the entire orchestration layer.