CVE-2026-12249 Canonical ADSys Trust Store Poisoning via Plaintext HTTP Certificate Auto-Enrollment
Man-in-the-middle attackers can poison the system trust store by intercepting plaintext HTTP certificate requests, enabling TLS interception on Ubuntu hosts.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-12249?
CVE-2026-12249 is a critical vulnerability in Canonical Ubuntu 20.04 LTS, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-348
Which versions are affected by CVE-2026-12249?
3 open source packages ship an affected version, including github.com/ubuntu/adsys.
| Package | Affected | Fixed in |
|---|---|---|
github.com/ubuntu/adsys Go | All versions | None |
github.com/ubuntu/adsys Go | All versions | 0.16.3-0.20250318112551-8b1939f96d38 |
github.com/ubuntu/adsys Go | All versions | 0.16.3-0.20250318112551-8b1939f96d38 |
How do I fix CVE-2026-12249?
Upgrade github.com/ubuntu/adsys to 0.16.3-0.20250318112551-8b1939f96d38 or later.
Is CVE-2026-12249 being exploited?
There is no known exploitation of CVE-2026-12249 in the wild and no public exploit code.
Sources
Also known as GHSA-crm4-q7v4-c2r2, GO-2026-6543, UBUNTU-CVE-2026-12249.