ruby net-imap up to 0.4.23/0.5.13/0.6.3 Net::IMAP blocking code in single-threaded, non-blocking context

Summaryinfo

A vulnerability described as problematic has been identified in ruby net-imap up to 0.4.23/0.5.13/0.6.3. Affected by this vulnerability is the function Net::IMAP. The manipulation results in use of blocking code in single-threaded, non-blocking context. This vulnerability is reported as CVE-2026-42256. The attack can be launched remotely. No exploit exists. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in ruby net-imap up to 0.4.23/0.5.13/0.6.3. It has been classified as problematic. Affected is the function Net::IMAP. The manipulation with an unknown input leads to a use of blocking code in single-threaded, non-blocking context vulnerability. CWE is classifying the issue as CWE-1322. The product uses a non-blocking model that relies on a single threaded process for features such as scalability, but it contains code that can block when it is invoked. This is going to have an impact on availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-42256 since 04/26/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available.

Upgrading to version 0.4.24, 0.5.14 or 0.6.4 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 158d0b505074397cdb5ceb58935e42dd2bcfa612 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the vulnerability database at CERT Bund (WID-SEC-2026-2117). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

• Red Hat Enterprise Linux
• RESF Rocky Linux
• HCL BigFix
• Oracle Linux

Productinfo

Type

• Programming Language Software

Vendor

• ruby

Name

• net-imap

Version

• 0.4.0
• 0.4.1
• 0.4.2
• 0.4.3
• 0.4.4
• 0.4.5
• 0.4.6
• 0.4.7
• 0.4.8
• 0.4.9
• 0.4.10
• 0.4.11
• 0.4.12
• 0.4.13
• 0.4.14
• 0.4.15
• 0.4.16
• 0.4.17
• 0.4.18
• 0.4.19
• 0.4.20
• 0.4.21
• 0.4.22
• 0.4.23
• 0.5.0
• 0.5.1
• 0.5.2
• 0.5.3
• 0.5.4
• 0.5.5
• 0.5.6
• 0.5.7
• 0.5.8
• 0.5.9
• 0.5.10
• 0.5.11
• 0.5.12
• 0.5.13
• 0.6.0
• 0.6.1
• 0.6.2
• 0.6.3

License

• open-source

Website

• Product: https://github.com/ruby/net-imap/

CPE 2.3info

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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