CVE-2024-26461: MIT Kerberos 5 Information Disclosure

CVE-2024-26461 Overview

CVE-2024-26461 is a memory leak vulnerability affecting MIT Kerberos 5 (krb5) version 1.21.2. The vulnerability exists within the /krb5/src/lib/gssapi/krb5/k5sealv3.c file, which is part of the GSSAPI (Generic Security Services Application Program Interface) implementation. This memory leak can be exploited remotely to exhaust system resources, leading to denial of service conditions on affected systems.

Critical Impact

This memory leak vulnerability can be exploited over the network without authentication to cause denial of service through resource exhaustion, potentially affecting critical authentication infrastructure.

Affected Products

• MIT Kerberos 5 version 1.21.2
• NetApp Active IQ Unified Manager for VMware vSphere
• NetApp Cloud Volumes ONTAP Mediator
• NetApp Management Services for Element Software and NetApp HCI
• NetApp ONTAP 9
• NetApp ONTAP Select Deploy Administration Utility
• NetApp H610C/H610S/H615C Firmware and Hardware

Discovery Timeline

• 2024-02-29 - CVE-2024-26461 published to NVD
• 2024-04-15 - NetApp releases security advisory NTAP-20240415-0011
• 2025-05-23 - Last updated in NVD database

Technical Details for CVE-2024-26461

Vulnerability Analysis

This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The memory leak occurs in the k5sealv3.c source file, which handles GSS-API version 3 sealing operations used in Kerberos authentication and secure message exchange.

Memory leaks in authentication libraries like Kerberos are particularly dangerous because these services typically run continuously as background daemons handling authentication requests. Over time, repeated exploitation can cause the Kerberos service to consume increasing amounts of memory, eventually leading to service degradation or complete unavailability.

The vulnerability can be triggered remotely over the network, requires no special privileges, and needs no user interaction to exploit. While the vulnerability does not allow for data theft or system compromise, its availability impact is significant as Kerberos is often a critical component in enterprise authentication infrastructure.

Root Cause

The root cause of CVE-2024-26461 is improper memory management in the GSSAPI sealing implementation. Specifically, memory allocations made during message sealing operations in k5sealv3.c are not properly freed under certain execution paths. This results in memory being allocated but never released back to the system, causing cumulative memory consumption over time.

The vulnerability falls under CWE-770 (Allocation of Resources Without Limits or Throttling), indicating that the code fails to properly limit resource allocation, allowing an attacker to trigger repeated allocations that eventually exhaust available memory.

Attack Vector

The attack vector for CVE-2024-26461 is network-based. An attacker can remotely send specially crafted requests to a vulnerable Kerberos service that trigger the memory leak condition. By repeatedly sending such requests, an attacker can cause the service to gradually consume all available system memory.

The attack does not require authentication (no privileges needed) and can be executed without any user interaction, making it suitable for automated exploitation. While each individual leak may be small, sustained attack traffic can lead to:

1. Progressive memory exhaustion on the Kerberos server
2. Service degradation as the system struggles with low memory
3. Complete denial of service when memory is fully exhausted
4. Potential cascading failures of dependent services relying on Kerberos authentication

Detection Methods for CVE-2024-26461

Indicators of Compromise

• Unusual or steadily increasing memory consumption by Kerberos-related processes (krb5kdc, kadmind)
• High volume of GSSAPI seal/unseal operations from single source IPs
• System logs indicating memory allocation failures or out-of-memory conditions
• Performance degradation in authentication services

Detection Strategies

• Monitor memory usage trends for Kerberos daemon processes over extended periods
• Implement anomaly detection for sudden spikes in Kerberos authentication traffic
• Set up alerts for memory consumption thresholds on authentication servers
• Review system logs for repeated memory-related errors from krb5 components

Monitoring Recommendations

• Deploy endpoint detection and response (EDR) solutions like SentinelOne to monitor process behavior and resource consumption
• Configure system monitoring to track memory usage patterns for krb5kdc and related processes
• Implement network monitoring to detect unusual patterns of Kerberos traffic
• Enable verbose logging on Kerberos services to capture potential exploitation attempts

How to Mitigate CVE-2024-26461

Immediate Actions Required

• Identify all systems running MIT Kerberos 5 version 1.21.2 in your environment
• Check for updates from MIT Kerberos project and apply available patches
• Review NetApp security advisory NTAP-20240415-0011 for affected NetApp products
• Consider implementing network-level rate limiting for Kerberos traffic as a temporary mitigation

Patch Information

Organizations should monitor the official MIT Kerberos project and vendor security advisories for patch availability. NetApp has acknowledged the vulnerability in their advisory NTAP-20240415-0011, which covers multiple NetApp products including Active IQ Unified Manager, Cloud Volumes ONTAP Mediator, ONTAP 9, and H-series firmware.

For detailed technical information about the vulnerability, refer to the GitHub krb5 Defects Documentation.

Workarounds

• Implement network segmentation to limit exposure of Kerberos services to trusted networks only
• Configure firewall rules to restrict access to Kerberos ports (88/TCP, 88/UDP, 749/TCP) from untrusted sources
• Set up automated service restarts if memory consumption exceeds safe thresholds as a temporary measure
• Consider deploying load balancers with health checks to detect and respond to memory exhaustion conditions

# Example: Monitor Kerberos process memory usage
#!/bin/bash
# Check memory consumption of krb5kdc daemon
watch -n 60 'ps aux | grep krb5kdc | grep -v grep | awk "{print \$6/1024 \" MB\"}"'

# Set up firewall rules to restrict Kerberos access (iptables example)
iptables -A INPUT -p tcp --dport 88 -s trusted_network/24 -j ACCEPT
iptables -A INPUT -p udp --dport 88 -s trusted_network/24 -j ACCEPT
iptables -A INPUT -p tcp --dport 88 -j DROP
iptables -A INPUT -p udp --dport 88 -j DROP