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How CVE-2026-53658 Works
Hyperledger Fabric Certificate Authority (CA) is a core component of the Hyperledger Fabric blockchain framework, responsible for issuing and managing digital identities. When Fabric CA is configured to use an LDAP backend for user authentication, it constructs an LDAP search filter to locate the user entry corresponding to the username provided in the HTTP Basic Authentication header. The username is taken directly from the `Authorization` header and inserted into the filter string without any sanitization or escaping per RFC 4515.
The vulnerable code path occurs before the password is validated. This means an unauthenticated attacker can send a specially crafted username to the CA enrollment endpoint (typically /enroll) and influence the LDAP query structure. By injecting LDAP filter metacharacters such as “, (, ), |, &, !, etc., the attacker can alter the logical conditions of the search. For example, a payload like `)(uid=admin` can be used to bypass the intended user lookup and force the LDAP query to return a different entry—often that of a privileged account like `admin` or cn=admin.
Because the password check is performed after the LDAP search, the attacker can then attempt to authenticate using the victim’s distinguished name (DN) that was returned by the manipulated filter. If the attacker knows or guesses the victim’s password (or exploits weak credentials), they can successfully log in as that victim. Even without knowing the password, the injection can be used to steer the authentication flow toward a specific account, potentially enabling brute‑force or password‑spraying attacks against high‑value identities.
The vulnerability affects all Fabric CA versions up to and including 1.5.20. The fix, released in version 1.5.21, introduces proper escaping of the username input before it is placed into the LDAP filter, neutralizing the injection vector. Users who do not use an LDAP backend are not impacted. The attack requires network access to the CA enrollment endpoint; if the endpoint is not exposed to untrusted networks, the risk is reduced. However, in typical production deployments, the CA is often accessible to peers, clients, and orderers, making this a serious concern.
DailyCVE Form:
Platform: Hyperledger Fabric CA
Version: <= 1.5.20
Vulnerability: LDAP Injection
Severity: Moderate
Date: 2026-06-03
Prediction: Patched in 1.5.21
What Undercode Say (Analytics & Detection)
Check your Fabric CA version
fabric-ca-server version
Verify if LDAP is enabled in your configuration
grep -i "ldap" /etc/hyperledger/fabric-ca-server/fabric-ca-server-config.yaml
Look for unescaped username usage in source code (vulnerable pattern)
grep -r "fmt.Sprintf.uid=%s" $GOPATH/src/github.com/hyperledger/fabric-ca/
Test for LDAP injection vulnerability using a crafted username
curl -X POST http://<ca-ip>:7054/enroll \
-H "Authorization: Basic $(echo -n ')(uid=admin):password' | base64)" \
-d '{"certificate_request":"..."}'
Exploit (Educational Purposes!)
An attacker can send a username like `)(uid=admin` in the Basic Auth header. The LDAP filter becomes (&(objectClass=person)(uid=)(uid=admin)), which may return the admin entry. If the attacker then provides a valid password for that admin (or uses a default/weak one), they gain full administrative access to the CA.
Protection from this CVE
- Upgrade to Fabric CA v1.5.21 or later immediately.
- If upgrading is not possible, restrict network access to the CA enrollment endpoint using firewalls or mutual TLS (mTLS) so that only trusted Fabric components can reach it.
- Enable HTTPS (TLS) to protect the Basic Authentication header in transit, though this does not prevent the injection itself—it only prevents eavesdropping.
- Monitor LDAP server logs for unusual search filters containing metacharacters.
Impact
- Authentication Bypass: An unauthenticated remote attacker can manipulate LDAP queries to impersonate any user known to the LDAP directory.
- Account Takeover: By steering the authentication toward a privileged account (e.g., admin), the attacker may gain full control over the CA, allowing them to issue, revoke, or manage certificates arbitrarily.
- Compromise of Blockchain Network: With CA privileges, an attacker can enroll rogue identities, join the network, and potentially subvert transaction ordering or endorsement policies.
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Sources:
Reported By: github.com
Extra Source Hub:
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