CVE-2007-0251 in Snort
Summary
by MITRE
Integer underflow in the DecodeGRE function in src/decode.c in Snort 2.6.1.2 allows remote attackers to trigger dereferencing of certain memory locations via crafted GRE packets, which may cause corruption of log files or writing of sensitive information into log files.
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Analysis
by VulDB Data Team • 08/17/2018
The vulnerability identified as CVE-2007-0251 represents a critical integer underflow condition within the Snort network intrusion detection system version 2.6.1.2. This flaw exists in the DecodeGRE function located in the src/decode.c source file, where improper handling of packet header fields can lead to unpredictable memory access patterns. The vulnerability specifically affects the GRE (Generic Routing Encapsulation) protocol decoding functionality, which is essential for Snort's ability to process and analyze network traffic containing encapsulated packets.
The technical implementation of this vulnerability stems from inadequate input validation within the DecodeGRE function where unsigned integer values are manipulated without proper bounds checking. When processing crafted GRE packets, the function performs arithmetic operations that can result in integer underflow conditions, causing the program to calculate negative or unexpectedly small values for buffer sizes or packet offsets. This miscalculation leads to memory access violations where the application attempts to read or write to memory locations that were not properly allocated or initialized. The underflow condition occurs when the system subtracts a value that exceeds the maximum representable value of the unsigned integer type, causing it to wrap around to a very large positive value or zero, ultimately resulting in memory corruption.
The operational impact of this vulnerability extends beyond simple memory corruption, as it creates potential for sensitive data exposure and log file manipulation. Remote attackers can exploit this condition to cause the Snort daemon to write arbitrary data to log files, potentially including sensitive system information, credentials, or other confidential data. The memory dereferencing issues can also result in application crashes or unexpected behavior that may disrupt network monitoring operations. According to CWE classification, this vulnerability maps to CWE-191 Integer Underflow (Wrap or Wraparound) which specifically addresses scenarios where integer arithmetic operations produce values that are outside the expected range of the data type, leading to security implications. The vulnerability also aligns with ATT&CK technique T1059 Command and Scripting Interpreter where attackers may leverage such memory corruption vulnerabilities to execute malicious code or manipulate system logs for evasion purposes.
Mitigation strategies for CVE-2007-0251 should prioritize immediate patching of the Snort 2.6.1.2 installation with the official security update released by the Snort development team. Organizations should implement network segmentation and access controls to limit exposure of Snort sensors to untrusted networks, as the vulnerability requires remote exploitation through crafted GRE packets. Network administrators should also enhance monitoring of log file integrity and implement automated alerting for suspicious log entries that may indicate exploitation attempts. Additional defensive measures include implementing network intrusion prevention systems that can detect and block malformed GRE traffic, enabling strict input validation for all protocol decoders, and conducting regular security assessments of network monitoring infrastructure. The vulnerability demonstrates the critical importance of proper integer overflow and underflow handling in security-critical applications, emphasizing the need for comprehensive input validation and boundary checking in all network protocol processing functions. Organizations should also consider implementing network traffic analysis tools that can identify and alert on unusual GRE packet patterns that may indicate attempted exploitation of similar vulnerabilities in other network security tools.