Scheduled for Leaks: Unmasking GitLab's Pipeline Authorization Bypass

In the modern DevOps landscape, the CI/CD pipeline is the nervous system of the organization. It builds, it tests, and most importantly, it deploys. To do that, it needs secrets: AWS keys, Kubernetes configs, and API tokens. GitLab stores these conveniently as CI/CD variables. Some are global, but others are tucked away inside Pipeline Schedules—mechanisms that allow jobs to run at specific intervals (like a cron job for your code).

Here is the problem: Schedules aren't just timers; they are contexts. They define how the pipeline runs, including the environment variables injected into the runtime. If you can read the schedule definition fully, you can often read the secrets required to run that schedule.

CVE-2025-14594 is a reminder that in the world of complex ACLs (Access Control Lists), granular permissions are often the first thing to break. The vulnerability allows an authenticated attacker—potentially just a Developer or even a Reporter on a project—to peek behind the curtain and view pipeline values they have no business seeing. It’s a classic case of "The front door is locked (you can't run the pipeline), but the window is open (you can read the schedule details)."

Technically, this is classified as CWE-639: Authorization Bypass Through User-Controlled Key. In the bug bounty world, we often shorthand this as an IDOR (Insecure Direct Object Reference), though it’s slightly more nuanced here due to the authorization context.

The vulnerability resides in the Pipeline Schedules API (GET /projects/:id/pipeline_schedules/:pipeline_schedule_id). When a request is made to this endpoint, the backend correctly identifies the project and the schedule. However, it fails to apply the correct policy scope to the response object.

In GitLab's architecture (Ruby on Rails + Grape API), retrieving an object usually involves a Finder class and a Policy check. The flaw here is a mismatch between access to the object and access to the object's sensitive attributes. The system effectively said, "Oh, you're a member of this project? Sure, you can see this schedule." It forgot to ask the follow-up question: "Wait, are you actually an Admin who should be allowed to see the encrypted variables inside it?"

The CVSS score of 3.5 (Low) with UI:R (User Interaction Required) is the real curveball. A standard API IDOR is usually UI:N. The presence of UI:R suggests that the attacker cannot simply curl the endpoint in isolation to get the goods. Instead, the attack likely relies on a CSRF-style vector or a state dependency where the victim (an Admin) must be tricked into triggering the data load, or the attacker utilizes a shared frontend state to bleed the data across privilege boundaries.

Let's look at the anatomy of the fix. In a typical GitLab API entity, data is exposed using a serializer. Vulnerabilities often creep in when sensitive fields are exposed unconditionally.

The patch, applied in commits like e529f6c3f048a1600ee184ee72f234cfd3ecbdb6 and 24b860ec8f94cded541e088aeff15552b46af805, introduces a strict check on the variables field. Before the fix, the code likely looked something like this (simplified for dramatic effect):

# VULNERABLE CODE (Conceptual)
expose :variables, using: Entities::Ci::Variable do |schedule, options|
  schedule.variables
end

This is the "Implicit Trust" model. If the user reached this block, the code assumed they were allowed to see everything. The fix shifts this to an "Explicit Trust" model, forcing a permission check at the field level:

# PATCHED CODE (Conceptual)
expose :variables, using: Entities::Ci::Variable, if: ->(schedule, options) {
  can?(options[:current_user], :admin_pipeline_schedule, schedule)
}

By wrapping the sensitive attribute in a can? check, GitLab ensures that even if a low-privileged user can query the schedule metadata (ID, description, next run time), the variables array returns null or is omitted entirely unless the user explicitly holds the admin_pipeline_schedule permission.

Because of the UI:R (User Interaction Required) constraint, we can't just script a mass-scanner to dump variables from every public GitLab instance. We have to get creative. The attack scenario likely involves Client-Side Enforcement Bypass or Cross-User Information Leak via CSRF.

The Attack Chain

1. Reconnaissance: The attacker (authenticated as a low-priv Reporter) identifies a target project containing sensitive pipeline schedules. They enumerate the Schedule IDs (which are often sequential integers).
2. The Trap: Since direct API access might be blocked or require a specific token, the attacker constructs a malicious page or a deceptive link pointing to the vulnerable GitLab instance.
3. The Trigger: The attacker tricks a Project Maintainer (Victim) into visiting a crafted URL or interacting with a specific page element. This interaction triggers the GET /pipeline_schedules request within the victim's session.
4. The Exfiltration: Through a secondary vulnerability (like a lax CORS policy or a specific XSS gadget on the page), or simply by observing the response in a shared context, the attacker captures the JSON response containing the variables block.

> [!NOTE] > Why this matters: Even though it requires interaction, this is a valid kill chain for targeted attacks. If I know your project uses a specific deployment token in a schedule, I can target your Maintainers specifically to leak that one credential.

Why panic over a 3.5 CVSS? Because CVSS measures severity, not value. The value of a CI/CD variable is binary: it's either useless, or it's root access to your cloud environment.

If an attacker successfully exploits this, they aren't just seeing that a schedule runs at 3:00 AM. They are potentially seeing:

• AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY
• PRODUCTION_DB_PASSWORD
• STRIPE_API_KEY

With these keys, the attacker bypasses the GitLab environment entirely. They don't need to modify the code; they can just log directly into your S3 buckets or your production database. The impact is a total compromise of the deployed infrastructure, essentially bypassing the entire software supply chain security perimeter.

Furthermore, since this affects the Enterprise Edition, high-value corporate targets are in the crosshairs. This is the kind of bug that sits quietly in a bug bounty report until a red teamer chains it with a low-impact XSS to burn down a production environment.

GitLab has released patches for the affected versions. If you are running a self-managed instance, you are the firewall. You need to upgrade immediately.

Patched Versions:

• 18.8.4
• 18.7.4
• 18.6.6

If you cannot upgrade immediately, mitigation is difficult because this is a logic flaw in the compiled code. Network-level WAF rules might help if you can block requests to pipeline_schedules from suspicious IPs, but since the attack requires authenticated user interaction, distinguishing legitimate traffic from malicious traffic is nearly impossible.

Lesson Learned: Developers, when exposing objects via API, never assume the parent object's permission implies the child attribute's permission. Always authorize at the leaf node of your data graph.