Portainer missing authorization on custom template file endpoint, which exposes template content

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.0 · CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-44884: 0.26% estimated exploitation activity in the next 30 days; percentile 17.45 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary A missing authorization vulnerability in the Custom Template file endpoint (GET /api/customtemplates/{id}/file) allows any authenticated user to read the file content of any custom template by enumerating sequential integer IDs, bypassing Resource Control access restrictions. Template files may contain environment-specific values such as connection strings, API tokens, or registry credentials that administrators would not expect standard users to read. Severity Medium CWE-862 — Missing Authorization Exploitation requires an authenticated user account and at least one custom template to exist. Template files are returned verbatim and may contain embedded credentials. Affected Versions The vulnerability exists in every Portainer release since custom templates were introduced — the customTemplateFile handler has never performed an authorization check. Fixes are included in the following releases: | Branch | First vulnerable | Fixed in |…

Published by the source

14 May 2026, 16:34 UTC

Last modified by the source

9 Jun 2026, 10:25 UTC

Source last checked

26 Oct 2026, 15:23 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-cqpq-2fgr-8mvc

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# Patch Next advisory brief: CVE-2026-44884

Advisory: Portainer missing authorization on custom template file endpoint, which exposes template content
IDs: CVE-2026-44884, GHSA-cqpq-2fgr-8mvc
Record: https://patchnext.com/advisories/cve-2026-44884 (revision 1, source checked 26 Oct 2026, 15:23 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/portainer/portainer 2.39.1, 2.33.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/portainer/portainer: affected >= 2.33.0, < 2.33.8; >= 2.39.0, < 2.39.1; fixed in 2.39.1, 2.33.8

## Suggested inspection (read-only)
- Go github.com/portainer/portainer: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/portainer/portainer.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cqpq-2fgr-8mvc (GitHub-reviewed advisory GHSA-cqpq-2fgr-8mvc lists affected ranges: Go github.com/portainer/portainer >=2.33.0 =2.39.0 <2.39.1)

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