CVE-2026-42256 Details
Description
Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. From versions 0.4.0 to before 0.4.24, 0.5.0 to before 0.5.14, and 0.6.0 to before 0.6.4, when authenticating a connection with SCRAM-SHA1 or SCRAM-SHA256, a hostile server can perform a computational denial-of-service attack on the client process by sending a big iteration count value. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.
A denial-of-service vulnerability has been identified in the Ruby Net::IMAP library, specifically in versions 0.4.0 prior to 0.4.24, 0.5.0 prior to 0.5.14, and 0.6.0 prior to 0.6.4. When using SCRAM-SHA1 or SCRAM-SHA256 for authentication, a malicious server can cause significant computational delays in the client by sending a large iteration count value. This exploitation takes advantage of the PBKDF2 function, which is a blocking operation in a C extension, effectively freezing the Ruby virtual machine and disrupting other running threads.
Users can upgrade to Net::IMAP versions 0.4.24, 0.5.14, or 0.6.4, all of which include the necessary fix. After upgrading, it's important to set the `max_iterations` parameter to a safe value when using SCRAM authentication.
Metrics
CVSS 4.0 Severity and Vector Strings:
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 11, 2026References to Advisories, Solutions, and Tools
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Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-1322 | Use of Blocking Code in Single-threaded, Non-blocking Context | [email protected] |
| CWE-770 | Allocation of Resources Without Limits or Throttling | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| ruby-lang net::imap | >= 0.4.0, < 0.4.24 >= 0.5.0, < 0.5.14 >= 0.6.0, < 0.6.4 |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jul 24, 2026 | CVE Translated | [email protected] |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 18, 2026 | Initial Analysis | [email protected] |
| May 9, 2026 | New CVE Received | [email protected] |