CVE-2020-15690 in Nim
Summary
by MITRE • 01/30/2021
In Nim before 1.2.6, the standard library asyncftpclient lacks a check for whether a message contains a newline character.
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Analysis
by VulDB Data Team • 08/18/2025
The vulnerability identified as CVE-2020-15690 affects the Nim programming language's standard library implementation of asynchronous ftp client functionality prior to version 1.2.6. This issue resides within the asyncftpclient module which handles ftp protocol communications in asynchronous programming contexts. The flaw represents a classic input validation weakness that can potentially lead to various security implications when processing ftp server responses or commands.
The technical root cause of this vulnerability stems from insufficient validation of message content within the ftp client implementation. Specifically, the asyncftpclient module fails to properly sanitize or validate incoming ftp messages for the presence of newline characters. This omission creates a potential vector for protocol manipulation attacks where malicious ftp servers could craft responses containing embedded newline characters that might be interpreted incorrectly by the client application. The absence of newline character validation means that the client does not properly handle message boundaries, potentially leading to parsing errors or injection vulnerabilities.
From an operational impact perspective, this vulnerability could enable attackers to manipulate ftp client behavior through crafted server responses. When the client processes ftp messages containing unexpected newline characters, it may misinterpret command boundaries or data sequences, potentially leading to command injection scenarios or protocol state corruption. The vulnerability is particularly concerning in environments where ftp clients handle untrusted server responses or when the client application is used in automated or security-critical contexts where reliable protocol handling is essential. This flaw could be exploited to bypass security controls or cause denial of service conditions within applications relying on the affected nim library.
The vulnerability aligns with CWE-704 which categorizes improper input validation as a weakness that can lead to various injection attacks and protocol manipulation scenarios. From an attack framework perspective, this issue could be classified under ATT&CK technique T1071.004 for application layer protocol manipulation, where attackers exploit protocol parsing weaknesses to gain unauthorized access or cause system instability. The vulnerability also relates to broader ftp protocol security considerations where proper input sanitization is critical for preventing various injection and manipulation attacks. Organizations using nim applications that employ the asyncftpclient module should prioritize updating to version 1.2.6 or later to mitigate this risk. The fix typically involves implementing proper validation of message content to ensure that newline characters are either properly escaped or rejected during message processing. Additionally, security teams should review applications using this library to ensure that proper error handling and input validation mechanisms are in place to prevent exploitation of similar vulnerabilities in other components of their ftp client implementations.