CVE-2010-0212 in OpenLDAP
Summary
by MITRE
OpenLDAP 2.4.22 allows remote attackers to cause a denial of service (crash) via a modrdn call with a zero-length RDN destination string, which is not properly handled by the smr_normalize function and triggers a NULL pointer dereference in the IA5StringNormalize function in schema_init.c, as demonstrated using the Codenomicon LDAPv3 test suite.
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Analysis
by VulDB Data Team • 12/29/2024
The vulnerability described in CVE-2010-0212 represents a critical denial of service flaw within OpenLDAP version 2.4.22 that demonstrates a classic null pointer dereference condition. This issue arises from improper input validation during the processing of modrdn (modify relative distinguished name) operations within the Lightweight Directory Access Protocol implementation. The flaw specifically manifests when a remote attacker submits a modrdn call containing a zero-length RDN (Relative Distinguished Name) destination string, which the software fails to properly handle during schema validation processes. The vulnerability exploits the smr_normalize function's inability to correctly process malformed input, leading to a cascade of failures that ultimately results in application crash and service unavailability.
The technical execution of this vulnerability occurs through the LDAP protocol's modrdn operation which is used to rename directory entries by modifying their relative distinguished names. When a zero-length RDN string is provided as a destination parameter, the schema validation logic fails to account for this edge case properly. The smr_normalize function, which is responsible for normalizing schema-related data, does not adequately validate the input string length before passing it to downstream processing functions. This leads to a NULL pointer dereference in the IA5StringNormalize function located within schema_init.c, where the software attempts to access memory at a null address, causing an immediate crash of the OpenLDAP daemon process. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions, and demonstrates how improper input validation can lead to complete service disruption.
The operational impact of this vulnerability extends beyond simple service interruption as it can be exploited remotely without authentication, making it particularly dangerous in production environments where OpenLDAP servers serve as critical infrastructure components for directory services. Organizations relying on OpenLDAP for user authentication, access control, and directory management may experience complete service outages when this vulnerability is successfully exploited. The attack vector is particularly concerning because it requires minimal privileges and can be automated, allowing for potential abuse in distributed denial of service scenarios or as part of broader exploitation campaigns targeting directory services. The vulnerability also aligns with ATT&CK technique T1499.004 which covers network denial of service attacks, specifically targeting services through malformed input processing.
Mitigation strategies for this vulnerability should include immediate patching of OpenLDAP installations to versions that properly handle zero-length RDN strings in modrdn operations. Organizations should also implement network-level protections such as firewall rules that limit LDAP traffic to trusted sources and consider implementing intrusion detection systems that can identify and block malformed LDAP requests. Additionally, monitoring and logging should be enhanced to detect unusual patterns of modrdn operations that might indicate exploitation attempts. The fix typically involves strengthening input validation within the smr_normalize function to properly handle edge cases including empty strings, and ensuring that all string processing functions validate input parameters before attempting memory operations. Security teams should also conduct regular vulnerability assessments of directory services and maintain updated threat intelligence feeds to identify similar patterns in other LDAP implementations that may be susceptible to analogous attacks.