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bdu:2026-08525

EUVD-2026-322788

fkie_cve-2026-44881

Portainer Community Edition is a lightweight service delivery platform for containerized applications that can be used to manage Docker, Swarm, Kubernetes and ACI environments. From 2.33.0 to before 2.33.8, 2.39.2, and 2.41.0, Portainer supports deploying stacks from Git repositories. When a Git-backed stack is created or updated, Portainer clones the repository using go-git v5, which translates Git blob entries with mode 0o120000 (symlink) into real OS symlinks on the host filesystem via os.Symlink. The only entry blocked from becoming a symlink is .gitmodules; every other path is created as a symlink without validation. Portainer's GET /api/stacks/{id}/file endpoint then reads the stack entry point with os.ReadFile, which follows OS symlinks transparently. A repository containing docker-compose.yml as a symlink to an arbitrary filesystem path causes the symlink target's contents to be returned verbatim in the HTTP response. Any authenticated user with rights to create or update a Git-backed stack — the default configuration in Portainer CE — can read arbitrary files accessible to the Portainer process. This vulnerability is fixed in 2.33.8, 2.39.2, and 2.41.0.

GHSA-rpgq-m5fp-32wr — Portainer Has an Arbitrary File Read via Git Symlink Injection in Stack Auto-Update

Affected: Go: github.com/portainer/portainer

## Summary Portainer supports deploying stacks from Git repositories. When a Git-backed stack is created or updated, Portainer clones the repository using `go-git` v5, which translates Git blob entries with mode `0o120000` (symlink) into real OS symlinks on the host filesystem via `os.Symlink`. The only entry blocked from becoming a symlink is `.gitmodules`; every other path — including `docker-compose.yml`, which Portainer treats as the stack entry point — is created as a symlink without validation.

Portainer's `GET /api/stacks/{id}/file` endpoint then reads the stack entry point with `os.ReadFile`, which follows OS symlinks transparently. A repository containing `docker-compose.yml` as a symlink to an arbitrary filesystem path (for example `/etc/passwd` or a mounted Kubernetes service account token) causes the symlink target's contents to be returned verbatim in the HTTP response. Any authenticated user with rights to create or update a Git-backed stack — the default configuration in Portainer CE — can read arbitrary files accessible to the Portainer process.

The issue is amplified by Git-stack auto-update: an attacker can create a stack from a legitimate repository, pass initial review, and later push a commit that replaces `docker-compose.yml` with a symlink; the file read is then triggered on the next scheduled update cycle with no further interaction required.

## Severity **High**

Attack complexity is Low: the attacker needs only the ability to host a Git repositor…