Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.5.7, 0.4.20, 0.3.9, and 0.2.5, there is a possibility for denial of service by memory exhaustion when net-imap reads server responses. At any time while the client is connected, a malicious server can send can send a literal byte count, which is automatically read by the clients receiver thread. The response reader immediately allocates memory for the number of bytes indicated by the server response. This should not be an issue when securely connecting to trusted IMAP servers that are well-behaved. It can affect insecure connections and buggy, untrusted, or compromised servers (for example, connecting to a user supplied hostname). This issue has been patched in versions 0.5.7, 0.4.20, 0.3.9, and 0.2.5.
The product does not properly control the allocation and maintenance of a limited resource.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Net::imap | Ruby-lang | * | 0.2.5 (excluding) |
| Net::imap | Ruby-lang | 0.3.0 (including) | 0.3.9 (excluding) |
| Net::imap | Ruby-lang | 0.4.0 (including) | 0.4.20 (excluding) |
| Net::imap | Ruby-lang | 0.5.0 (including) | 0.5.7 (excluding) |
| Jruby | Ubuntu | focal | * |
| Jruby | Ubuntu | oracular | * |
| Ruby2.7 | Ubuntu | focal | * |
| Ruby3.3 | Ubuntu | oracular | * |
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.