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Net\Application · Ruby Lang

CVE-2026-42258

MEDIUM · 5.3 CVSS v3.1 Published 2026-05-09
Fix available
A fix is available. Upgrade to 0.4.24 / 0.5.14 or later.
See remediation →
55/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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, symbol arguments to commands are vulnerable to a CRLF Injection / IMAP Command injection via Symbol arguments passed to IMAP commands. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Net::IMAP Ruby library before versions 0.4.24, 0.5.14, and 0.6.4 is vulnerable to CRLF injection via symbol arguments passed to IMAP commands. Attackers can inject arbitrary IMAP commands by crafting malicious symbol arguments due to insufficient input sanitization.

MitigationUpgrade Net::IMAP to version 0.4.24, 0.5.14, or 0.6.4 or later. Review code that passes symbol arguments to IMAP commands and validate/sanitize all user-controlled input before use.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Net\Application
Affected:< 0.4.24>= 0.5.0, < 0.5.14>= 0.6.0, < 0.6.4

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
Low

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Net::IMAP version
    Run `gem list net-imap` or inspect your Gemfile.lock for the net-imap gem version, or use `ruby -e "require 'net/imap'; puts Net::IMAP::VERSION"`
    Affected if The version is below 0.4.24, or in the range 0.5.x < 0.5.14, or 0.6.x < 0.6.4
  2. Identify IMAP command usage with symbol arguments
    Search your codebase for IMAP method calls that use symbols as arguments, such as `imap.search`, `imap.fetch`, `imap.store`, or `imap.status` where the argument could be user-controlled
    Affected if Your code passes user-supplied or untrusted input directly as symbol arguments to IMAP commands without sanitization
  3. Review input handling before IMAP symbols
    Audit how user input reaches IMAP command symbol arguments; check if input is validated, allowlisted, or converted to safe types before being passed to Net::IMAP methods
    Affected if User-provided values flow directly into symbol arguments without validation, making CRLF injection possible

You are affected if you have a vulnerable Net::IMAP version AND your application passes untrusted input as symbol arguments to IMAP commands without sanitization.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 0.4.24 / 0.5.14 / 0.6.4 or later
Fixed in 0.4.240.5.140.6.4
Interim mitigation

Upgrade Net::IMAP to version 0.4.24, 0.5.14, or 0.6.4 or later. Review code that passes symbol arguments to IMAP commands and validate/sanitize all user-controlled input before use.

Recommended fix High confidence

Upgrade to net-imap version 0.4.24, 0.5.14, or 0.6.4 depending on your current version branch

  1. 1. Identify the current version of the Net::IMAP gem by running `gem list net-imap` or checking your Gemfile.lock
  2. 2. Determine which version branch you are currently on (0.4.x, 0.5.x, or 0.6.x)
  3. 3. Upgrade to the appropriate patched version: if using 0.4.x, upgrade to 0.4.24; if using 0.5.x, upgrade to 0.5.14; if using 0.6.x, upgrade to 0.6.4
  4. 4. Run `gem install net-imap -v VERSION` or update your Gemfile with the new version and run `bundle update net-imap`
  5. 5. Test your application to ensure IMAP functionality works correctly after the upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Net\ Scoped from the published advisory
  • Consultation2.0 h
  • Implementation1.0 h
  • Testing3.0 h
  • Review / QA2.0 h
8.0 hours of engineering $1,390
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-42258 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data