PatchSiren cyber security CVE debrief

CVE-2026-44881 portainer CVE debrief

Portainer Community Edition versions 2.33.0 through 2.33.7, 2.39.x before 2.39.2, and 2.41.0 contain a path traversal vulnerability via symlink following. The application uses go-git v5 to clone Git repositories for stack deployment, which creates OS-level symlinks for Git blob entries with mode 0o120000. Only .gitmodules is blocked; all other paths become symlinks without validation. The GET /api/stacks/{id}/file endpoint uses os.ReadFile, which follows symlinks transparently. An authenticated user with rights to create or update Git-backed stacks (default in Portainer CE) can craft a repository with docker-compose.yml as a symlink pointing to arbitrary filesystem paths, causing the target file contents to be returned in HTTP responses. This allows arbitrary file read access with the privileges of the Portainer process.

Vendor: portainer
Product: Unknown
CVSS: HIGH 8.5
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-05-28
Original CVE updated: 2026-05-29
Advisory published: 2026-05-28
Advisory updated: 2026-05-29

Who should care

Organizations running Portainer Community Edition versions 2.33.0-2.33.7, 2.39.x before 2.39.2, or 2.41.0 with Git-backed stack deployment enabled; security teams managing container orchestration platforms; DevOps engineers with stack management privileges

Technical summary

The vulnerability exists in Portainer CE's Git-backed stack deployment feature. When cloning repositories, go-git v5 translates Git symlinks (mode 0o120000) to OS symlinks without adequate validation. The stack file retrieval endpoint follows these symlinks using os.ReadFile, enabling authenticated users to read arbitrary files accessible to the Portainer process by crafting malicious Git repositories with symlinked compose files.

Defensive priority

HIGH

Recommended defensive actions

Upgrade Portainer Community Edition to version 2.33.8, 2.39.2, or 2.41.0 or later
Restrict Git-backed stack creation and update privileges to administrative users only
Implement repository content validation before stack deployment
Monitor for suspicious stack creation or update activities involving external Git repositories
Review access logs for unexpected file access patterns via the /api/stacks/{id}/file endpoint

Evidence notes

Vulnerability confirmed via GitHub Security Advisory GHSA-rpgq-m5fp-32wr. CVSS 4.0 vector: AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:H/SA:H. CWE-59 (Improper Link Resolution Before File Access) and CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor) identified. Fixed versions: 2.33.8, 2.39.2, 2.41.0.

Official resources

2026-05-28