GHSA-hm49-wcqc-g2xg

Summary

Several Net::IMAP commands accept a raw string argument that is sent to the server without validation or escaping. If this string is derived from user-controlled input, it may contain contain CRLF sequences, which an attacker can use to inject arbitrary IMAP commands.

Details

Net::IMAP's generic argument handling, used by most command arguments, interprets string arguments as an IMAP astring. Depending on the string contents and the connection's UTF-8 support, this encodes strings as either a atom, quoted, or literal. These are safe from command or argument injection.

But the following commands transform specific String arguments to Net::IMAP::RawData, which bypasses normal argument validation and encoding and prints the string directly to the socket:

• #uid_search, #search
  • when criteria is a String, it is sent raw
• #uid_fetch, #fetch
  • when attr is a String, it is sent raw
  • when attr is an Array, each String in attr is sent raw
• #uid_store, #store
  • when attr is a String, it is sent raw
• #setquota:
  • limit is interpolated with #to_s and that string is sent raw

Because these string arguments are sent without any neutralization, they serve as a direct vector for command splitting. Any user controlled data interpolated into these strings can be used to break out of the intended command context.

Using "raw data" arguments for #uid_store, #store, and #setquota I both inappropriate and unnecessary. Net::IMAP's generic argument handling is sufficient to safely validate and encode their arguments. Users of the library probably do not expect arguments to these commands to be sent raw and might not be wary of passing unvalidated input.

The API for search criteria and fetch attributes is intentionally low-level and "close to the wire". It allows developers to use some IMAP extensions without requiring explicit support from the library and allows developers to use complex IMAP...