---
id: CVE-2026-12249
aliases:
  - GHSA-crm4-q7v4-c2r2
title: Canonical ADSys Uses a Less Trusted Source
summary: Canonical ADSys Uses a Less Trusted Source
severity: critical
cvss: 9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H'
vendor: ubuntu
product: github.com/ubuntu/adsys
ecosystem: go
affected:
  - github.com/ubuntu/adsys < 0.16.3-0.20250318112551-8b1939f96d38
patched:
  - github.com/ubuntu/adsys 0.16.3-0.20250318112551-8b1939f96d38
published: '2026-06-22'
updated: '2026-09-21'
sourceUpdated: '2026-09-21T22:30:13.168372166Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-crm4-q7v4-c2r2'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-12249'
  - url: >-
      https://github.com/ubuntu/adsys/commit/8b1939f96d3827b4426eb06c1ced5bf317b0a99d
  - url: 'https://github.com/ubuntu/adsys'
  - url: 'https://github.com/ubuntu/adsys/releases/tag/v0.16.3'
  - url: 'https://ubuntu.com/security/CVE-2026-12249'
  - url: 'https://github.com/advisories/GHSA-crm4-q7v4-c2r2'
tags:
  - osv
  - go
  - ghsa
epss: 0.00143
epssPercentile: 0.0294
cwe:
  - CWE-348
ingestedAt: '2026-09-21T22:54:37.975Z'
---

## Overview

An issue was discovered in Canonical ADSys upstream versions through v0.16.2. During Active Directory Certificate Services (AD CS) certificate auto-enrollment via the vendored Samba client script (internal/policies/certificate/python/vendor_samba/gp/gp_cert_auto_enroll_ext.py), ADSys utilizes a plaintext HTTP connection (http://) instead of a secure HTTPS connection (https://) to request the CA certificate from the Active Directory Certificate Services server (GetCACert). An unauthenticated network attacker positioned between the managed Ubuntu host and the configured AD CS CA hostname can conduct a Man-in-the-Middle (MITM) attack. By intercepting the plaintext HTTP request, the attacker can supply an arbitrary, attacker-controlled Root CA certificate. Because the system automatically accepts this certificate and registers it into the local system trust store via update-ca-certificates, this results in system-wide trust store poisoning. Consequently, TLS clients utilizing the operating system trust store on the affected machine will accept rogue certificates for arbitrary domains, enabling persistent decryption and interception of subsequent TLS connections. This issue is resolved in version v0.16.3.

## Affected packages

- `github.com/ubuntu/adsys < 0.16.3-0.20250318112551-8b1939f96d38`

## Remediation

Upgrade to a patched release:

- `github.com/ubuntu/adsys 0.16.3-0.20250318112551-8b1939f96d38`