---
title: CVE-2026-12249
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2026-12249
---

# CVE-2026-12249

Publication date 22 June 2026

Last updated 26 June 2026

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**8.3 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2026-12249#impact-score)

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## 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.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| adsys | 26.04 LTS resolute | Not affected |
| 25.10 questing | Fixed 0.16.3 |
| 24.04 LTS noble | Not affected |
| 22.04 LTS jammy | Not affected |
| 20.04 LTS focal | Not affected |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Severity score breakdown

CVSS version:

CVSS v4.0

[CVSS v4.0](https://ubuntu.com/security/CVE-2026-12249)
[CVSS v3.0](https://ubuntu.com/security/CVE-2026-12249)

**Base score**

9.0 · Critical

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | High |
  | Attack requirements | None |
  | Privileges required | None |
  | User interaction | None |
  | Vulnerable system - Confidentiality impact | High |
  | Vulnerable system - Integrity impact | High |
  | Vulnerable system - Availability impact | High |
  | Subsequent system - Confidentiality impact | High |
  | Subsequent system - Integrity impact | High |
  | Subsequent system - Availability impact | High |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 9.0 · Critical |
  | Base + Threat score | - |
  | Base + Environmental score | - |
  | Base + Threat + Environmental score | - |

**Vector:** CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P/S:N/AU:Y/R:I/V:D/RE:L/U:Red

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-12249)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-12249)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-12249)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-12249)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-12249>