Source: cve@mitre.org
Snort 1.6, when running in straight ASCII packet logging mode or IDS mode with straight decoded ASCII packet logging selected, allows remote attackers to cause a denial of service (crash) by sending non-IP protocols that Snort does not know about, as demonstrated by an nmap protocol scan.
Snort 1.6, a popular intrusion detection system, is vulnerable to a denial-of-service (DoS) attack. By sending crafted network packets using unknown protocols, attackers can crash the Snort process, rendering it unable to detect and respond to malicious activity, thus creating a security gap.
Step 1: Packet Crafting: An attacker crafts network packets using protocols that Snort 1.6 does not recognize. This is easily achieved using tools like nmap with protocol scanning capabilities. Step 2: Packet Transmission: The attacker sends these crafted packets to the network segment monitored by the vulnerable Snort instance. Step 3: Snort Processing: Snort receives the packets and, due to its configuration (straight ASCII logging or IDS mode with ASCII logging), attempts to decode and log the packet data. Step 4: Protocol Mismatch: Because Snort doesn't know the protocol, it encounters unexpected data. Step 5: Crash: The unexpected data causes Snort to crash, resulting in a denial-of-service.
The vulnerability stems from Snort's handling of unknown, non-IP protocols when configured for straight ASCII packet logging or IDS mode with ASCII logging. The root cause is a lack of proper input validation and error handling when processing these unknown protocols. Specifically, Snort attempts to decode and log these packets, but because it doesn't know the protocol, it likely encounters unexpected data structures or formats. This leads to a crash, possibly due to an unhandled exception or a memory access violation. The specific function or logic flaw is likely within the packet decoding and logging routines, where the absence of protocol-specific parsing logic allows malformed or unexpected data to trigger the crash. This is not a buffer overflow or race condition but a logic error related to protocol handling.
While no specific APTs are directly linked to this vulnerability, its simplicity and the widespread use of Snort make it a potential target for any attacker seeking to disrupt network monitoring. The vulnerability's age and the availability of PoCs mean it could be leveraged by various threat actors. This CVE is not listed in the CISA KEV catalog.
Network traffic analysis: Look for unusual network traffic using non-standard or unknown protocols, especially if originating from external sources.
Log analysis: Examine Snort logs for error messages or crashes. Specifically, look for log entries indicating protocol decoding errors or unexpected data formats.
System monitoring: Monitor the Snort process for unexpected termination or high CPU/memory usage.
IDS alerts: Implement custom Snort rules to detect the specific packets that trigger the vulnerability. These rules would look for traffic using unknown protocols.
Upgrade to a patched version of Snort (1.8 or later) or a more recent version of Suricata, which is a modern alternative.
Disable straight ASCII packet logging if possible. This reduces the attack surface.
Implement protocol-specific parsing logic for any custom or non-standard protocols used in the network (if applicable).
Harden the Snort configuration by limiting the types of traffic it processes and by implementing strict input validation.
Regularly update Snort's rule sets to include the latest threat signatures.
Implement network segmentation to isolate critical systems and limit the impact of a successful DoS attack.