Use of Blocking Code in Single-threaded, Non-blocking Context Affecting net-imap package, versions >=0.4.0, <0.4.24>=0.5.0, <0.5.14>=0.6.0, <0.6.4


Severity

Recommended
0.0
high
0
10

CVSS assessment by Snyk's Security Team. Learn more

Threat Intelligence

EPSS
0.05% (15th percentile)

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  • Snyk IDSNYK-RUBY-NETIMAP-16420124
  • published6 May 2026
  • disclosed4 May 2026
  • creditMasamune

Introduced: 4 May 2026

NewCVE-2026-42256  (opens in a new tab)
CWE-1322  (opens in a new tab)
CWE-770  (opens in a new tab)

How to fix?

Upgrade net-imap to version 0.4.24, 0.5.14, 0.6.4 or higher.

Overview

Affected versions of this package are vulnerable to Use of Blocking Code in Single-threaded, Non-blocking Context through the OpenSSL::KDF.pbkdf2_hmac function during SCRAM authentication. An attacker can cause the Ruby client VM to become unresponsive by sending a large iteration count value from a malicious server, resulting in prolonged computation and blocking all Ruby threads.

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

  • High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

  • Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

CVSS Base Scores

version 4.0
version 3.1