CVE-2026-60108 in Zeek
Summary
by MITRE • 07/09/2026
Zeek before 8.0.9 contains an uncontrolled memory consumption vulnerability in the FTP analyzer that allows unauthenticated remote attackers to cause process termination by sending a crafted FTP control session negotiating AUTH GSSAPI followed by a large ADAT control line. Attackers can exploit the NVT_Analyzer component's lack of a maximum line length check, causing it to continuously double its internal buffer without bounds during base64 decoding of an attacker-controlled ADAT token, resulting in denial of service of the Zeek sensor.
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Analysis
by VulDB Data Team • 07/09/2026
The vulnerability under analysis represents a critical memory exhaustion issue affecting Zeek versions prior to 8.0.9, specifically within the FTP analyzer component. This flaw resides in the NVT_Analyzer module responsible for processing network traffic, particularly targeting the FTP protocol's authentication mechanisms. The vulnerability manifests when an unauthenticated remote attacker crafts a specific sequence of FTP control commands that exploit a fundamental design oversight in buffer management. The attack vector involves initiating an FTP session with AUTH GSSAPI negotiation followed by a deliberately crafted ADAT control line containing an oversized base64-encoded token.
The technical implementation of this vulnerability stems from the absence of input validation mechanisms within the NVT_Analyzer component, specifically failing to enforce maximum line length constraints during FTP control message processing. When the system encounters the malicious ADAT control line, it begins base64 decoding operations on the attacker-controlled data without any bounds checking on buffer expansion. The internal buffer management algorithm continuously doubles its allocated memory size during the base64 decoding process, creating an exponential growth pattern that rapidly consumes available system resources. This behavior directly maps to CWE-770, which addresses allocation of resources without proper limits, and represents a classic example of uncontrolled resource consumption leading to denial of service conditions.
The operational impact of this vulnerability extends beyond simple service disruption, as it can cause complete process termination of the Zeek sensor daemon, effectively removing network monitoring capabilities from the affected system. The attack requires minimal privileges since it targets an unauthenticated FTP control session, making it particularly dangerous for network environments where FTP services are exposed to external networks. The resource exhaustion occurs rapidly during the base64 decoding phase, meaning that even a single malicious connection can trigger the denial of service condition. This vulnerability aligns with ATT&CK technique T1499.004, which describes resource exhaustion attacks targeting network monitoring systems, and represents a significant threat to network security operations centers relying on Zeek for traffic analysis.
Mitigation strategies for this vulnerability include immediate deployment of Zeek version 8.0.9 or later, which implements proper bounds checking and maximum line length validation for FTP control messages. Organizations should also consider implementing network-level controls such as firewall rules that restrict FTP service access to trusted networks, and deploy intrusion detection systems that can identify and block malicious FTP control sequences. The fix addresses the root cause by introducing defensive programming practices including buffer size limits, input validation checks, and proper resource management within the FTP analyzer component. Additionally, network administrators should consider implementing rate limiting mechanisms for FTP control sessions and monitoring for unusual memory consumption patterns in Zeek processes, particularly during periods of high network activity when such attacks might be attempted.