389 Directory Server Heap Buffer Overflow Vulnerability in schema_attr_enum_callback Function Allowing Denial-of-Service and Potential Remote Code Execution

A heap buffer overflow vulnerability has been identified in the 389 Directory Server (389-ds-base) within the schema_attr_enum_callback function of the schema.c file. This vulnerability arises from improper buffer size calculations, as the code sums alias string lengths without considering additional formatting characters. When a large number of aliases are processed, this can lead to a heap overflow, potentially allowing a remote attacker to cause a denial-of-service or execute arbitrary code. Exploitation requires high privileges on the Directory Server, limiting the attack surface to authenticated administrative users.

Impact

Exploitation of this vulnerability can lead to a heap-based buffer overflow, causing crashes and resource consumption issues. Additionally, such buffer overflows can be exploited to execute arbitrary code, bypassing the application's security mechanisms and potentially allowing unauthorized access or control over the system.

Reproduction

The vulnerability can be reproduced by processing a large number of alias strings in the 389 Directory Server. The schema_attr_enum_callback function will incorrectly calculate the buffer size, leading to a heap buffer overflow. This can be done by manipulating schema attributes to include excessive aliases, which will trigger the overflow when the formatting overhead exceeds the static buffer limit.

Remediation

It is recommended to restrict network access to the 389-ds-base server to trusted hosts and networks, using firewall rules. Additionally, administrative access should be limited to authorized personnel with strong authentication, as exploitation of this vulnerability requires high privileges.