Integer Overflow in 389 Directory Server Leading to Heap Buffer Overflow

Executive Summary

CVE-2026-11774 is an integer overflow vulnerability in the SASL I/O layer of the 389 Directory Server (389-ds-base). It occurs when a specially crafted SASL packet with a length prefix of 0xFFFFFFFC is processed, causing an unsigned integer wraparound to zero in the sasl_io_start_packet() function. This bypasses the configured maximum SASL I/O packet size limit (nsslapd-maxsasliosize) and leads to a heap buffer overflow of up to approximately 2 megabytes of attacker-controlled data.

After a successful SASL bind with integrity protection, a remote attacker who is authenticated can exploit this flaw to cause a Denial of Service (DoS) or potentially achieve Remote Code Execution (RCE). The vulnerability affects FreeIPA and Red Hat Identity Management deployments, where any domain user with a valid Kerberos ticket, enrolled host, or service account can trigger the issue remotely.

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Compliance Impact

The vulnerability in the 389 Directory Server SASL I/O layer allows authenticated users to cause a denial of service or potentially achieve remote code execution. This could lead to unauthorized access or disruption of directory services that manage user authentication and identity information.

Such unauthorized access or service disruption could impact compliance with standards and regulations like GDPR and HIPAA, which require protection of personal data and system availability. Specifically, the risk of remote code execution or denial of service could lead to data breaches or service outages, violating confidentiality, integrity, and availability requirements.

However, the provided information does not explicitly detail compliance impacts or mitigation measures related to these standards.

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Impact Analysis

This vulnerability can have serious impacts including causing a Denial of Service (DoS) by crashing the LDAP server, which disrupts directory services and authentication processes.

More critically, on certain older platforms such as Red Hat Enterprise Linux 8 with glibc 2.28, it can be exploited to achieve Remote Code Execution (RCE), allowing an attacker to run arbitrary code on the affected server.

Since the vulnerability can be triggered remotely by any authenticated domain user with a valid Kerberos ticket or service account, it poses a significant risk in environments using FreeIPA or Red Hat Identity Management.

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Detection Guidance

Detection of this vulnerability involves monitoring for abnormal SASL packet lengths and unexpected crashes or behavior in the 389 Directory Server (389-ds-base). Specifically, look for SASL packets with a length prefix of 0xFFFFFFFC, which triggers the integer overflow.

Since the vulnerability is triggered by specially crafted SASL packets, network traffic analysis tools can be used to inspect LDAP SASL bind requests for suspicious packet sizes.

Commands to help detect potential exploitation attempts might include:

• Using tcpdump or Wireshark to capture and filter LDAP traffic, for example: tcpdump -i <interface> -s 0 -w ldap_capture.pcap port 389
• Analyzing captured packets in Wireshark to inspect SASL bind requests for unusually large or suspicious length prefixes.
• Checking server logs for crashes or abnormal terminations of the 389 Directory Server process.
• Using system monitoring tools to detect unexpected process restarts or high memory usage that could indicate exploitation attempts.

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Mitigation Strategies

Immediate mitigation steps include restricting access to the 389 Directory Server to trusted users only, especially limiting SASL bind operations to trusted domain users.

Since the vulnerability requires authenticated SASL binds, enforcing stricter authentication policies and monitoring for unusual SASL bind activity can reduce risk.

Applying any available patches or updates from the vendor as soon as they are released is critical.

If patching is not immediately possible, consider temporarily disabling SASL authentication or limiting the maximum SASL I/O size settings if configurable, to reduce the attack surface.

Monitoring server stability and logs for signs of exploitation attempts and preparing incident response plans are also recommended.

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