Source: cve@mitre.org
Integer overflow in gopher daemon (gopherd) 3.0.3 allows remote attackers to cause a denial of service and possibly execute arbitrary code via crafted content of a certain size that triggers the overflow.
Gopherd, a legacy information retrieval protocol daemon, is vulnerable to an integer overflow that can lead to a denial-of-service (DoS) and potentially remote code execution (RCE). Attackers can exploit this vulnerability by sending a specially crafted request with a large content size, triggering the overflow and crashing the service or allowing for arbitrary code execution. This vulnerability, while old, could still be present in legacy systems and pose a significant risk if exploited.
Step 1: Request Submission: The attacker sends a crafted Gopher request to the gopherd server. This request includes a content size field.
Step 2: Integer Overflow Trigger: The attacker crafts the content size field to contain a value that, when processed by gopherd, causes an integer overflow.
Step 3: Size Calculation Error: Due to the overflow, the server calculates an incorrect content size, typically a much smaller value than the actual content size.
Step 4: Memory Allocation: The server allocates memory based on the incorrect, smaller size.
Step 5: Content Write: The server attempts to write the malicious content to the allocated buffer.
Step 6: Buffer Overflow: Because the allocated buffer is smaller than the actual content size, a buffer overflow occurs. The attacker's crafted content overwrites adjacent memory regions.
Step 7: Code Execution (Potential): If the attacker has carefully crafted the overflow, they can overwrite critical data structures, such as function pointers, and redirect the program's execution flow to arbitrary code, achieving remote code execution. Alternatively, the overflow can corrupt data, leading to a crash and denial-of-service.
The vulnerability lies within gopherd 3.0.3's handling of content sizes. Specifically, the code likely uses an integer variable to store the size of the content received from a client. When a malicious client sends a request with a content size exceeding the maximum value that the integer can hold, an integer overflow occurs. This leads to a wrap-around of the integer value, resulting in an incorrect size being used in subsequent memory allocation or processing operations. This can lead to a buffer overflow or other memory corruption issues. The root cause is the lack of proper input validation and size checking before performing arithmetic operations or memory allocation. The incorrect size calculation can then be used to allocate insufficient memory, leading to a heap overflow when the content is written to the buffer. This overflow can overwrite adjacent memory regions, potentially allowing an attacker to overwrite critical data structures, including function pointers, and achieve remote code execution. The specific function or logic flaw is likely related to how the content size is read, validated, and used in memory allocation or processing.
Due to the age of the vulnerability, it's less likely to be actively targeted by sophisticated APTs. However, it could be used in opportunistic attacks or by less sophisticated actors. The vulnerability's presence in legacy systems could make it a target for attackers seeking to gain initial access or escalate privileges. No specific APT groups are directly linked to this vulnerability. Not listed in CISA KEV.
Monitor network traffic for unusual Gopher requests, especially those with large content sizes or suspicious payloads.
Analyze server logs for crashes or unexpected behavior related to gopherd.
Implement file integrity monitoring to detect changes to gopherd binaries or configuration files.
Use intrusion detection systems (IDS) with signatures for known gopherd exploits.
Examine memory dumps or core files after a crash to identify the root cause and any evidence of exploitation.
Upgrade to a patched version of gopherd or a more secure alternative.
If upgrading is not possible, disable the gopherd service if it is not required.
Implement input validation to ensure that content sizes are within acceptable limits.
Apply security patches provided by the vendor.
Harden the server by disabling unnecessary services and restricting network access.
Implement a Web Application Firewall (WAF) to filter malicious requests.