CVE-2026-42568

An LDAP injection vulnerability exists in org.yamcs.security.LdapAuthModule when constructing search filters. The username parameter is inserted directly into the LDAP filter without proper RFC 4515 escaping.

Root Cause

File: yamcs-core/src/main/java/org/yamcs/security/LdapAuthModule.java:233

The username parameter is inserted directly into an LDAP search filter without RFC 4515 escaping:

// VULNERABLE
var filter = userFilter.replace("{0}", username);
var searchResult = getSingleResult(ctx, userBase, filter, controls);

LDAP wildcard characters (*, (, )) are accepted without sanitization.

Proof of Concept

curl -X POST "http://TARGET:8090/auth/token" \
  -d "grant_type=password&username=*&password=known_password"
# Returns token for first matching LDAP user

With a known valid password, username=* authenticates as the first user returned by the LDAP search, enabling horizontal privilege escalation between accounts sharing similar passwords or when the attacker knows one valid password.

This affects deployments that use org.yamcs.security.LdapAuthModule in their etc/security.yaml configuration file.

CVE-2026-42568 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

Apply RFC 4515 escaping before filter construction:

private static String escapeLdapFilter(String input) {
    return input
        .replace("\\", "\\5c")
        .replace("*",  "\\2a")
        .replace("(",  "\\28")
        .replace(")",  "\\29")
        .replace("\0", "\\00");
}
var filter = userFilter.replace("{0}", escapeLdapFilter(username));

1. What is CVE-2026-42568? CVE-2026-42568 is a medium-severity security vulnerability in org.yamcs:yamcs-core (maven), affecting versions < 5.12.7. It is fixed in 5.12.7.
2. How severe is CVE-2026-42568? CVE-2026-42568 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-2026-42568? org.yamcs:yamcs-core (maven) versions < 5.12.7 is affected.
4. Is there a fix for CVE-2026-42568? Yes. CVE-2026-42568 is fixed in 5.12.7. Upgrade to this version or later.
5. Is CVE-2026-42568 exploitable, and should I be worried? Whether CVE-2026-42568 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-2026-42568 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-2026-42568? Upgrade org.yamcs:yamcs-core to 5.12.7 or later.