Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to 0.6.5 and 0.5.15, when Net::IMAP#id is called with a hash argument, although the ID field value strings are correctly quoted (escaping quoted specials), they were not validated to prohibit CRLF sequences. While Net::IMAP#enable does process its arguments for aliases, it does not validate them as valid atoms (or as a list of valid atoms). The #to_s value is sent verbatim. Arguments to either command could be used by an attacker to inject arbitrary IMAP commands. This vulnerability is fixed in 0.6.5 and 0.5.15.
PUBLISHED5.2CWE-77CWE-93
Net::IMAP: Command Injection via ID command argument
Problem type
- CWE-77: Improper Neutralization of Special Elements used in a Command ('Command Injection')
- CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')
Affected products
ruby
net-imap
>= 0.6.0, < 0.6.4.1 - AFFECTED
< 0.5.15 - AFFECTED
References
GitHub Security Advisories
GHSA-46q3-7gv7-qmgg
Net::IMAP: Command Injection via ID command argument
https://github.com/advisories/GHSA-46q3-7gv7-qmggSummary
Two Net::IMAP commands, #id and #enable, do not validate their arguments. Arguments to either command could be used by an attacker to inject arbitrary IMAP commands.
Please note that passing untrusted inputs to these commands is usually inappropriate and expected to be uncommon.
Details
When Net::IMAP#id is called with a hash argument, although the ID field value strings are correctly quoted (escaping quoted specials), they were not validated to prohibit CRLF sequences.
While Net::IMAP#enable does process its arguments for aliases, it does not validate them as valid atoms (or as a list of valid atoms). The #to_s value is sent verbatim.
Impact
This is expected to impact very few users: use of untrusted user input for either command is expected to be very uncommon.
The documentation for #enable explicitly warns that using any arguments that are not in the explicitly supported list may result in undocumented behavior. Using arbitrary untrusted user input for #enable will always be inappropriate.
Although client ID field values will most commonly be static and hardcoded, dynamic input sources may be used. For example, client ID fields may be set by configuration or version numbers. Using untrusted user inputs for client ID fields is expected to be uncommon. But any untrusted inputs to client ID can trivially exploit this vulnerability.
Untrusted inputs to either command may include a CRLF sequence followed by a new IMAP command (like DELETE mailbox). Although this does not directly enable data exfiltration, it could be combined with other attack vectors or knowledge of the target system's attributes, e.g.: shared mail folders or the application's installed response handlers.
Mitigation
Update to a version of net-imap which validates #id and #enable arguments.
Untrusted inputs should never be used for #enable arguments.
If net-imap cannot be upgraded:
- do not use untrusted inputs for client ID field values
- or add validation that client ID field values must not contain any CR or LF bytes.
JSON source
https://cveawg.mitre.org/api/cve/CVE-2026-47242Click to expand
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"dateUpdated": "2026-06-22T20:19:41.222Z",
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