# CVE-2026-47240: Ruby Net::IMAP command injection via non-synchronizing literals

Source: https://junglewise.ai/threats/cve-2026-47240-ruby-net-imap-command-injection-via-non-synchronizing-literals  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-06-22. Updated: 2026-06-22  
License: CC BY 4.0 with a link back

CVE-2026-47240 · Severity: medium · CVSS 4 · Published 2026-06-22

The Ruby net-imap library, which allows applications to communicate with email servers, contains a flaw in how it handles certain data commands. If an application using this library passes unvalidated user input to specific email search or fetch functions, an attacker could inject unauthorized commands. This could allow an attacker to perform unintended actions on the email server, such as deleting mailboxes or modifying folder structures, depending on the server's configuration.

Technologies: [net-imap (RubyGems)](https://junglewise.ai/threats/technologies/net-imap). Vendors: [RubyGems](https://junglewise.ai/threats/vendors/rubygems).

## Quick answers

**Is CVE-2026-47240 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-47240 being exploited in the wild.

**How severe is CVE-2026-47240?** Medium severity, with a CVSS score of 4, published 22 June 2026.

**Which products and versions are affected?** net-imap (RubyGems) ECOSYSTEM:introduced=0.6.0,fixed=0.6.4.1.

**Is there a fix for CVE-2026-47240?** Yes. net-imap (RubyGems): upgrade to 0.6.4.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-47240 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-47240?** Check whether you run net-imap (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- net-imap (RubyGems): upgrade to 0.6.4.1 or later

  ```sh
  bundle update net-imap
  ```


## Technical details

A CRLF injection vulnerability exists in Net::IMAP's handling of 'raw data' arguments for commands including #search, #sort, #thread, and #fetch. The root cause is the library's failure to validate server support for non-synchronizing literals (LITERAL+, LITERAL-, or IMAP4rev2) before sending them. If a server does not support these literals, it may interpret the '+}\r\n' sequence as the end of a malformed command and treat the subsequent literal content as new, pipelined IMAP commands. An attacker providing unvalidated input to these methods can execute arbitrary IMAP commands, such as DELETE. The vulnerability is fixed in versions 0.6.4.1 and 0.5.15.

## Affected products

- ruby net-imap >= 0.6.0, < 0.6.4.1; < 0.5.15

## Identifiers

- CVE-2026-47240
- GHSA-8p34-64r3-mwg8

## Timeline

- 2026-06-09: advisory: GitHub advisory GHSA-8p34-64r3-mwg8 published
- 2026-06-22: disclosed: CVE-2026-47240 published to NVD

## References

- [https://github.com/ruby/net-imap/security/advisories/GHSA-8p34-64r3-mwg8](https://github.com/ruby/net-imap/security/advisories/GHSA-8p34-64r3-mwg8)

## Related threats

- [Ruby Net::IMAP command injection in ID and ENABLE commands](https://junglewise.ai/threats/cve-2026-47242-ruby-net-imap-command-injection-in-id-and-enable-commands)
- [Ruby Net::IMAP denial of service via incomplete raw argument validation](https://junglewise.ai/threats/cve-2026-47241-ruby-net-imap-denial-of-service-via-incomplete-raw-argument)
- [Ruby Net::IMAP command injection via Symbol arguments](https://junglewise.ai/threats/cve-2026-42258-ruby-net-imap-command-injection-via-symbol-arguments)
- [Ruby Net::IMAP command injection in multiple commands](https://junglewise.ai/threats/cve-2026-42257-ruby-net-imap-command-injection-in-multiple-commands)
- [Ruby Net::IMAP computational DoS in SCRAM authentication](https://junglewise.ai/threats/cve-2026-42256-ruby-net-imap-computational-dos-in-scram-authentication)