Summary
Net::IMAP: Command Injection via ID command argument
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.
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.
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.
Untrusted input is inserted into a command that is later executed by the application, allowing the attacker to alter the intent of that command. Typical impact: arbitrary command execution in the application's environment.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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net-imap to 0.6.4.1 or later; net-imap to 0.5.15 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-47242? CVE-2026-47242 is a medium-severity command injection vulnerability in net-imap (rubygems), affecting versions >= 0.6.0, <= 0.6.4. It is fixed in 0.6.4.1, 0.5.15. Untrusted input is inserted into a command that is later executed by the application, allowing the attacker to alter the intent of that command.
- Which versions of net-imap are affected by CVE-2026-47242? net-imap (rubygems) versions >= 0.6.0, <= 0.6.4 is affected.
- Is there a fix for CVE-2026-47242? Yes. CVE-2026-47242 is fixed in 0.6.4.1, 0.5.15. Upgrade to this version or later.
- Is CVE-2026-47242 exploitable, and should I be worried? Whether CVE-2026-47242 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-47242 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-47242?
- Upgrade
net-imapto 0.6.4.1 or later - Upgrade
net-imapto 0.5.15 or later
- Upgrade