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

Summary

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.

Timeline

1. May 28, 2026, 9:11 PM UTCCVE published
2. May 29, 2026, 2:47 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. May 29, 2026, 2:47 PM UTCRecord last updated

Affected versions

• portainer portainer

  From 2.33.0 · fixed in 2.33.8; From 2.39.0 · fixed in 2.39.2; From 2.40.0 · fixed in 2.41.0

• github.com/portainer/portainerGo

  All versions

• github.com/portainer/portainerGo

  From 2.33.0 · fixed in 2.33.8

• github.com/portainer/portainerGo

  From 2.39.0 · fixed in 2.39.2

• github.com/portainer/portainerGo

  From 2.40.0 · fixed in 2.41.0

References 2