critical CVSS 9.9 EPSS 0.42%

CVE-2026-44881·Docker vulnerability

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.

Severity
critical
Software
Docker
Fixed in
2.39.2
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.42% — higher than 34% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-44881 scores 9.9 on CVSS, so a successful attack would be serious — but at 0.42%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

From: 2.34.0

Until: 2.39.2

Fixed in: 2.39.2

How to fix this CVE

Docker users should upgrade to version 2.39.2 or later to patch a critical symlink traversal vulnerability in Portainer that allows authenticated users to read arbitrary files from the host system. This vulnerability affects Docker deployments that use Portainer Community Edition for managing Git-backed stacks. Immediate patching is strongly recommended due to the high severity (CVSS 9.9) and the ease with which authenticated attackers can exploit this flaw to access sensitive files.

sudo dnf update docker-ce

Defensia detects this vulnerability

What an exploitation attempt looks like

Sample log line indicative of exploitation attempts:

GET /api/stacks/[0-9]+/file HTTP/1.1.*with symlink targets pointing to /etc/passwd|/etc/shadow|/root/.ssh|/proc/self/environ|/var/log|sensitive paths

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Implement WAF rules to block GET requests to /api/stacks/*/file endpoints that originate from non-administrative source IPs, enforce strict authentication token validation, and monitor for repeated requests to the same endpoint with different stack IDs as indicators of reconnaissance activity.

How to check if you are affected

  1. Check installed Docker version: docker --version and docker version
  2. Verify Portainer version if deployed: Check the Portainer web UI footer or run docker ps | grep portainer to identify the container version
  3. Search Portainer logs for suspicious GET /api/stacks/{id}/file requests: docker logs <portainer-container-id> | grep '/api/stacks' | grep 'GET'
  4. Confirm the patch by verifying Docker and Portainer versions match 2.39.2 or later: docker inspect <portainer-container-id> | grep 'Image' or check the release notes

Indicators of compromise

  • Symlink entries in Git repository docker-compose.yml files pointing to /etc/passwd, /etc/shadow, or other sensitive system paths
  • Suspicious GET requests to /api/stacks/{id}/file endpoint returning unexpected file content (non-YAML/JSON responses)
  • Git repositories cloned by Portainer containing 0o120000 mode entries in .git/objects

FAQ

What is CVE-2026-44881?

CVE-2026-44881 is a critical symlink traversal vulnerability in Portainer Community Edition that allows authenticated users to bypass file access restrictions by creating Git-backed stacks containing symlinks to arbitrary filesystem paths, enabling unauthorized file reads from the host system.

Is CVE-2026-44881 being actively exploited?

No, CVE-2026-44881 is not currently listed on the CISA KEV catalog as actively exploited, and no public exploits are known to be in circulation.

What versions of Docker are affected by CVE-2026-44881?

Portainer Community Edition versions 2.33.0 through 2.39.1 are vulnerable. Docker itself is not directly affected; the vulnerability exists in Portainer's stack deployment logic.

How do I check if my server is vulnerable to CVE-2026-44881?

Run 'docker ps | grep portainer' to identify Portainer containers, then inspect the image tag or check the Portainer UI dashboard footer to confirm the version. If it is below 2.39.2, 2.33.8, or 2.41.0, your system is vulnerable.

Does Defensia detect CVE-2026-44881?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Docker and Portainer are deployed on a monitored server, CVE-2026-44881 will appear in your dashboard with remediation steps.

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References

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