CVE-2026-60109 in Zeek
Summary
by MITRE • 07/09/2026
Zeek before 8.0.9 contains a null pointer dereference vulnerability in its Kerberos protocol analyzer that allows unauthenticated remote attackers to crash the sensor by sending a crafted KRB_ERROR message with error-code 25 (KDC_ERR_PREAUTH_REQUIRED) containing a PA-DATA element with padata-type 2, 3, 11, or 19. Attackers can exploit a parser and analyzer state mismatch where proc_padata() dereferences an uninitialized pa_data_element field selected by the wrong parsing arm, triggering a crash via a single UDP or TCP packet to port 88 without any credentials or prior authentication.
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Analysis
by VulDB Data Team • 07/09/2026
The vulnerability under discussion represents a critical null pointer dereference flaw in Zeek's Kerberos protocol analyzer affecting versions prior to 8.0.9. This issue stems from an inconsistent state management between the parser and analyzer components within the Kerberos protocol handling mechanism. The vulnerability specifically targets the processing of KRB_ERROR messages with error-code 25, which indicates that pre-authentication is required by the Key Distribution Center. When an attacker crafts a malicious KRB_ERROR message containing a PA-DATA element with padata-type values of 2, 3, 11, or 19, the system experiences a crash due to improper memory handling during protocol analysis.
The technical execution of this vulnerability occurs through a parser and analyzer state mismatch that fundamentally undermines the integrity of the Kerberos protocol processing module. The proc_padata() function attempts to dereference an uninitialized pa_data_element field when the parsing logic selects the incorrect processing arm based on the padata-type value. This particular mismatch between parsing decisions and memory initialization creates a scenario where a null pointer is accessed, leading to immediate system termination. The vulnerability operates at the network level through standard UDP or TCP packets directed at port 88, which is the default Kerberos service port, making it particularly dangerous as it requires no authentication credentials or prior access to the system.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a potential vector for more sophisticated attacks within network monitoring environments. Zeek sensors deployed in production networks become immediately vulnerable to remote exploitation without any authentication requirements, creating a significant risk for organizations relying on Zeek for security monitoring and threat detection. The crash occurs with a single packet, making this vulnerability particularly effective for rapid disruption attacks and potentially allowing attackers to establish persistent denial of service conditions against network monitoring infrastructure. This weakness directly affects the availability of security monitoring capabilities, which could mask other malicious activities or prevent detection of legitimate threats.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term architectural improvements to prevent similar state management issues. Organizations should prioritize upgrading to Zeek version 8.0.9 or later where the null pointer dereference has been patched. Network administrators should also consider implementing network segmentation and access controls that limit exposure of Zeek sensors to untrusted networks, particularly regarding port 88 traffic. The vulnerability aligns with CWE-476 which describes null pointer dereference conditions, and represents a clear example of how protocol analyzer implementations can introduce instability through improper state management. From an ATT&CK perspective, this vulnerability maps to T1499.004 (Network Denial of Service) and demonstrates the importance of maintaining robust protocol analysis components that cannot be easily destabilized by crafted network traffic, as highlighted in the broader category of T1595 (Active Scanning) where attackers might probe for such vulnerabilities before launching more sophisticated attacks.