Is CVE-2026-42257 in the CISA KEV catalog?

No. CVE-2026-42257 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-42257?

CVE-2026-42257 has a CVSS v3 base score of 9.8 (Moderate).

What is the EPSS score for CVE-2026-42257?

CVE-2026-42257 has an EPSS score of 0.43% (35th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-42257?

Upgrade ruby3 on rhel 8 to 3-main@aarch64 or later. Fixes are available for 8 affected products.

CVE & CISA-KEV Catalog

CVE-2026-42257

MEDIUM

9.8

CVSS v3

NVD

Description

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.4.24, 0.5.14, and 0.6.4, several Net::IMAP commands accept a raw string argument that is sent to the server without validation or escaping. If this string is derived from user-controlled input, it may contain contain CRLF sequences, which an attacker can use to inject arbitrary IMAP commands. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.

CWE-77Command Injection CWE-93

How to fix

Remediation Available

ruby3Red Hat / RHEL

Fixed in:3-main@aarch64RHSA-2026:40380

Fixed in:4-main@noarchRHSA-2026:38694

Fixed in:3-main@noarchRHSA-2026:40380

Fixed in:4-main@aarch64RHSA-2026:38694

Fixed in:4-main@x86_64RHSA-2026:38694

Fixed in:3-main@x86_64RHSA-2026:40380

Fixed in:4-main@srcRHSA-2026:38694

Fixed in:3-main@srcRHSA-2026:40380

ruby3Rocky

Fixed in:3-main@aarch64RHSA-2026:40380

Fixed in:4-main@aarch64RHSA-2026:38694

Fixed in:4-main@x86_64RHSA-2026:38694

Fixed in:3-main@srcRHSA-2026:40380

Fixed in:4-main@noarchRHSA-2026:38694

Fixed in:4-main@srcRHSA-2026:38694

Fixed in:3-main@noarchRHSA-2026:40380

Fixed in:3-main@x86_64RHSA-2026:40380

ruby4Red Hat / RHEL

Fixed in:0-main@aarch64RHSA-2026:36978

Fixed in:0-main@x86_64RHSA-2026:36978

Fixed in:0-main@noarchRHSA-2026:36978

Fixed in:0-main@srcRHSA-2026:36978

ruby4Rocky

Fixed in:0-main@aarch64RHSA-2026:36978

Fixed in:0-main@x86_64RHSA-2026:36978

Fixed in:0-main@noarchRHSA-2026:36978

Fixed in:0-main@srcRHSA-2026:36978

libruby2.3Ubuntu

Fixed in:2.3.1-2~ubuntu16.04.16+esm14USN-8431-1

libruby2.5Ubuntu

Fixed in:2.5.1-1ubuntu1.16+esm8USN-8431-1

ruby2.3Ubuntu

Fixed in:2.3.1-2~ubuntu16.04.16+esm14USN-8431-1

ruby2.5Ubuntu

Fixed in:2.5.1-1ubuntu1.16+esm8USN-8431-1

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityLow

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploit Intelligence

0.43%probability of exploitation in 30 days

35thpercentile

Low risk: more likely to be exploited than 35% of all known CVEs.

References

Vendor Advisory1

github.com

Release Notes3

Related Vulnerabilities

Other CWE-77 (Command Injection) vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2024-3400	Critical	10.0	100%	KEV + Ransom	-
CVE-2024-21887	Critical	9.1	100%	KEV + Ransom	-
CVE-2023-1671	Critical	9.8	100%	KEV	Fix
CVE-2023-1389	High	8.8	100%	KEV	Fix
CVE-2021-1498	Critical	9.8	100%	KEV	Fix
CVE-2012-1823	Critical	9.8	100%	KEV	Fix

Embed a live status badge for CVE-2026-42257

Markdown

[![CVE-2026-42257](https://tridentstack.com/cve/badge/CVE-2026-42257.svg)](https://tridentstack.com/cve/CVE-2026-42257)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-42257"><img src="https://tridentstack.com/cve/badge/CVE-2026-42257.svg" alt="CVE-2026-42257"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

See how it works Start freeThis CVE lookup is free and always will be.

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-05-18.