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Fencer Vulns
critical 9.0

CVE-2026-12249 json

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

published 2026-06-22 4 mo ago modified 2026-09-28 41 d ago also GHSA-crm4-q7v4-c2r2 , GO-2026-6543 , EUVD-2026-38297

cvss
9.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 3%
public exploits
0
none known

Summary

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.

Patch / fix

  • go github.com/ubuntu/adsys 0.16.3-0.20250318112551-8b1939f96d38
  • Canonical Ubuntu 22.04 LTS 0.16.3~22.04.2ubuntu0.22.04.1
  • Canonical Ubuntu 24.04 LTS 0.16.3~24.04.2ubuntu0.24.04.1
  • adsys Ubuntu 25.10 0.16.3

ubuntu advisories UBUNTU-CVE-2026-12249

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
4 mo ago

Exploit prediction

0.14% chance of exploitation in the next 30 days, higher than 3% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.3 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
CNA 4.0 9.0 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
CNA 4.0 9.0 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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:N/AU:Y/R:I/V:D/RE:L/U:Red
GitHub 3.1 9.0 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
go github.com/ubuntu/adsys
<0.16.3-0.20250318112551-8b1939f96d38
all versions
0.16.3-0.20250318112551-8b1939f96d38

Affected products

  • Canonical Ubuntu 20.04 LTS
  • Canonical Ubuntu 22.04 LTS
  • Canonical Ubuntu 24.04 LTS
  • Canonical Ubuntu 25.10
  • Canonical Ubuntu 26.04 LTS

Classification

Weakness
  • CWE-348 Use of Less Trusted Source

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.