CVE-2026-12391 — ubuntu-pro-client Local Privilege Escalation and Information Disclosure via Symlink Arbitrary File Read in collect-logs
An insecure symlink following vulnerability exists in Canonical ubuntu-pro-client (formerly ubuntu-advantage-tools) within the pro collect-logs command framework. The utility creates or utilizes predictable temporary file paths or user-accessible log directories when gathering diagnostic information without verifying the file type or ownership. An unprivileged local attacker can exploit this behavior by creating a symbolic link (symlink) at a predictable destination path pointing to an arbitrary, root-readable file (such as /etc/shadow or private files within /root). When a root administrator or operator subsequently executes the pro collect-logs command, the tool follows the user-controlled symlink, reads the target file, and compresses its contents into the resulting diagnostic support archive. Because the output archive remains readable by the unprivileged user, the attacker can extract and read the sensitive root-owned files, leading to a complete information disclosure of system secrets.
Who exploits it and how urgent it is
A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.
How the score was calculated
- EPSS 0.2% (30-day exploitation probability)+1
- Technical severity (medium)+3
The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).
Triage
Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.
CISA SSVC assessment CISA
Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.
Remediation
Fixes and mitigations documented by the sources — linked to the original advisory.
No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.
First 24 hours
Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.
- Identify exposed assets running the affected vendor/product/version combinations (Canonical Ubuntu 16.04 LTS, Canonical Ubuntu 18.04 LTS, Canonical Ubuntu 20.04 LTS…).
- No fix documented in the sources: reduce exposure and monitor the vendor advisory.
- Exploitation requires user interaction: tighten email/web filtering and warn affected users.
- Search available logs for exploit probes matching the vulnerability class (file handling), errors and authentication anomalies.
Affected scope
Vendor, product and versions as the sources word them.
| Vendor | Product | Versions | Status | Source |
|---|---|---|---|---|
| Canonical | Ubuntu 16.04 LTS | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Canonical | Ubuntu 18.04 LTS | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Canonical | Ubuntu 20.04 LTS | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Canonical | Ubuntu 22.04 LTS | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Canonical | Ubuntu 24.04 LTS | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Canonical | Ubuntu 26.04 LTS | versions not specified by the source | Vulnerable | CVE Program (cve.org) e CISA ADP |
| Canonical | Ubuntu-pro-client (ubuntu-advantage-tools) | < 37.3 | Vulnerable | CVE Program (cve.org) e CISA ADP |
Attack characteristics
The CVSS vector, decoded. It describes the attack, not your exposure to it.
Every base score collected
Sources score independently and may disagree; each row says who scored it and under which version.
| Score | Version | Severity | Expl. | Impact | Scored by |
|---|---|---|---|---|---|
| 5.0 | CVSS 3.1 | Medium | 1.3 | 3.6 | security@ubuntu.com via NIST National Vulnerability Database |
| 5.0 | CVSS 3.1 | Medium | — | — | canonical via CVE Program (cve.org) e CISA ADP |
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N (score shown at the top: security@ubuntu.com) Weakness MITRE
Weakness class according to MITRE’s CWE catalog.
Detection
Read off the CVSS vector and the weakness class. Starting points, not tested rules.
- Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
- Monitor file creation in web directories and paths with traversal sequences (../).
Timeline
What happened to this CVE, newest first.
- 2026
- Affected products added · canonical/ubuntu-pro-client (ubuntu-advantage-tools), canonical/ubuntu 26.04 lts, canonical/ubuntu 24.04 lts, canonical/
- SSVC assessment updated
- Record published
- CVSS changed · 5.0
- Source status changed · → Awaiting Analysis
- Record created in this database
- CVE published
Source activity
Repeated readings are counted rather than listed.
- 1× Official description updated · Oct 15, 2026 – Oct 15, 2026
References
1 on the record
Elsewhere on this site
Related CVEs (same products)
- High CVE-2026-8933 snap-confine Local Privilege Escalation via Capabilities Misconfiguration or Flaw in Execution Environment Setup Jul 21, 2026
- High CVE-2026-15226 snapd snap-confine Sandbox Confinement Bypass via Omission of setuid Restriction in Seccomp Templates Jul 21, 2026
- Medium CVE-2024-5300 AppArmor Base Profile Misconfiguration in snapd Permits Confined Snaps Unauthorized Access to Hashed Passwords via systemd-userdbd Jul 21, 2026
- Medium CVE-2026-9494 ubuntu-pro-client Information Disclosure via Cleartext Bearer Token Exposure in Process Command Line Jul 16, 2026
- Critical CVE-2026-11386 ubuntu-pro-client Input Validation Vulnerability Leading to Arbitrary APT Directive Injection and Remote Code Execution Jul 16, 2026
- Critical CVE-2026-12249 Canonical ADSys plaintext HTTP CA certificate retrieval enables trust store poisoning Jun 22, 2026
Not in any source we poll
Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.
- No fixed version, patch or mitigation documented.
- No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
- No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
- No exploit packet captures, log samples, or incident case IDs supplied.
Answered from this record
Text assembled only from the fields above — no additional claims.
What should defenders know first?
CVE-2026-12391 is "ubuntu-pro-client Local Privilege Escalation and Information Disclosure via Symlink Arbitrary File Read in collect-logs", rated Medium. It affects Ubuntu 16.04 LTS (Canonical); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.0 describes technical severity. EPSS 0.21% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.
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