Vulnerability · Published Jun 22, 2026 · Assigned by canonical
CVE-2026-12249Canonical ADSys Trust Store Poisoning via Plaintext HTTP Certificate Auto-Enrollment
High 8.3
In plain English
A high-severity security flaw in adsys. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 4% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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 & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Go | github.com/ubuntu/adsys | 0.16.3-0.20250318112551-8b1939f96d38 | GHSA-crm4-q7v4-c2r2 |
| Go | github.com/ubuntu/adsys | no fix listed | GO-2026-6543 |
| Ubuntu:25.10 | adsys | 0.16.3 | UBUNTU-CVE-2026-12249 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| adsys | 0.13.0 – before 0.16.3 | |
| Canonical | Ubuntu 20.04 LTS | see references |
| Canonical | Ubuntu 22.04 LTS | see references |
| Canonical | Ubuntu 24.04 LTS | see references |
| Canonical | Ubuntu 25.10 | see references |
| Canonical | Ubuntu 26.04 LTS | see references |
Weakness: CWE-348 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
References
- https://ubuntu.com/security/CVE-2026-12249 vdb-entry, issue-tracking
- https://github.com/ubuntu/adsys/commit/8b1939f96d3827b4426eb06c1ced5bf317b0a99d patch