# CVE-2026-12391: ubuntu-pro-client Local Privilege Escalation and Information Disclosure via Symlink Arbitrary File Read in collect-logs

> Local attackers can read root-owned files via symlink attacks in the pro collect-logs command, leading to information disclosure and potential privilege escalation.

- **Severity:** Medium 5.0 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 16 Jul 2026
- **Updated:** 16 Jul 2026
- **Also known as:** GHSA-whf7-7mxf-ww93, UBUNTU-CVE-2026-12391

## What is CVE-2026-12391?

CVE-2026-12391 is a medium-severity path traversal vulnerability in Canonical Ubuntu 16.04 LTS, published on 16 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

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.

Weakness: CWE-59 (Improper Link Resolution Before File Access)

## Which versions are affected by CVE-2026-12391?


## How do I fix CVE-2026-12391?

Apply the vendor's patch.

## Is CVE-2026-12391 being exploited?

There is no known exploitation of CVE-2026-12391 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-12391 and fix it if it is affected.

What it is: CVE-2026-12391 is a medium-severity path traversal vulnerability in Canonical Ubuntu 16.04 LTS, published on 16 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-12391 in the wild and no public exploit code.

Affected product: Canonical Ubuntu 16.04 LTS. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-12391/ (Markdown: https://insights.sbomify.com/CVE-2026-12391/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-12391
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-12391
- OSV: https://osv.dev/vulnerability/CVE-2026-12391

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-12391/
Summaries are generated and may contain mistakes; the official description above is the record.