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How the CVE Works:
The vulnerability exists within the `g_cfg.MaxUsers` configuration parsing component of LightFTP server version 2.0. This component is responsible for setting the maximum number of concurrent users. It uses a fixed-size buffer to store the value read from the configuration file. When the server reads a configuration line for MaxUsers, it does not perform proper bounds checking on the input data. An attacker can craft a configuration file or a network request that delivers an excessively long string for the MaxUsers parameter. This long string overflows the finite stack or heap buffer allocated for this purpose. The overflow corrupts adjacent memory, which can overwrite critical control data or instruction pointers. Ultimately, this corruption leads to an application crash, causing a Denial of Service (DoS). In more sophisticated attacks, the overflow could potentially allow for arbitrary code execution by precisely overwriting the function return address or a structured exception handler, giving the attacker control over the server process.
Platform: LightFTP
Version: 2.0
Vulnerability: Buffer Overflow
Severity: High
Date: 2025-12-01
Prediction: 2025-12-20
What Undercode Say:
Analytics:
strings lightftp | grep -i maxusers gcc -fstack-protector-all -D_FORTIFY_SOURCE=2 -o test test.c valgrind --tool=memcheck ./lightftp
How Exploit:
1. Attacker sends crafted `SET MaxUsers` command.
2. Command contains overly long string (>512 bytes).
3. Buffer overflow corrupts adjacent memory.
4. EIP overwritten, causing crash or code execution.
Protection from this CVE:
1. Apply vendor patch.
2. Use compile-time canaries (/GS flag).
3. Implement input length validation.
4. Run service with low privileges.
Impact:
1. Service Denial of Service.
2. Potential remote code execution.
3. System instability and crashes.
4. Unauthorized system access.
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Sources:
Reported By: nvd.nist.gov
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