High 8.3Published Jun 22, 2026

CVE-2026-12249Canonical ADSys Trust Store Poisoning via Plaintext HTTP Certificate Auto-Enrollment

Updated under an hour ago (Oct 27, 2026, 12:10 PM ET)

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It affects Canonical Ubuntu 20.04 LTS and 4 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Every CVE for Canonical Ubuntu 20.04 LTS

Exploited in the last 30 days

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.

CVSS: 8.3 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Weakness (CWE): CWE-348
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: canonical
NVD analysis: Awaiting Analysis
Record last updated: Jun 22, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Canonical Ubuntu 20.04 LTS canonical:ubuntu_20.04_lts (from the name)	0.9.2~20.04.2ubuntu0.1+esm2 not affected	CNA record
Canonical Ubuntu 22.04 LTS canonical:ubuntu_22.04_lts (from the name)	0.16.3~22.04.2ubuntu0.22.04.1 not affected	CNA record
Canonical Ubuntu 24.04 LTS canonical:ubuntu_24.04_lts (from the name)	0.16.3~24.04.2ubuntu0.24.04.1 not affected	CNA record
Canonical Ubuntu 25.10 canonical:ubuntu_25.10 (from the name)	0.16.3 not affected	CNA record
Canonical Ubuntu 26.04 LTS canonical:ubuntu_26.04_lts (from the name)	0.16.4ubuntu1 not affected	CNA record

References

References

https://ubuntu.com/security/CVE-2026-12249	vdb-entry, issue-tracking
https://github.com/ubuntu/adsys/commit/8b1939f96d3827b4426eb06c1ced5bf317b0a99d	patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.