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CVE Record

CVE-2026-42258: net-imap: Command Injection via unvalidated Symbol inputs

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.

HighCVSS 7.1Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

CVE-2026-42258 affects Ruby’s net-imap library. Vulnerable versions can mishandle Symbol values passed into IMAP commands, allowing injected line breaks to alter the IMAP command stream. Business risk is highest for Ruby applications that let external input influence IMAP command arguments.

Executive priority

Treat this as a high-priority dependency remediation for Ruby services that interact with IMAP. Patch quickly where exposure is confirmed, but avoid assuming compromise without separate evidence of exploitation.

Technical view

The issue is CRLF injection and IMAP command injection in net-imap Symbol arguments. Affected ranges are <0.4.24, >=0.5.0 <0.5.14, and >=0.6.0 <0.6.4. CVSS 3.1 is 7.1 with network attack vector, low complexity, no privileges, and user interaction required.

Likely exposure

Exposure is likely limited to Ruby applications or packaged software using affected net-imap versions and passing attacker-influenced values as Symbols to IMAP commands. Systems not using net-imap, or only using patched versions, are not indicated as affected by the provided sources.

Exploitation context

The provided bundle does not show KEV listing or confirmed active exploitation. Exploitation requires a reachable application path where user-controlled or attacker-influenced data becomes a Symbol argument to net-imap commands.

Researcher notes

Focus validation on data-flow from request, mailbox, configuration, or job input into net-imap command Symbol arguments. The sources identify fixed versions but do not provide exploit telemetry, affected downstream applications, or broader mitigation beyond upgrading and vendor advisories.

Mitigation direction

  • Upgrade net-imap to 0.4.24, 0.5.14, 0.6.4, or later applicable versions.
  • Apply relevant Red Hat advisories where net-imap is supplied by Red Hat packages.
  • Audit code for attacker-influenced Symbol arguments passed to IMAP commands.
  • Check vendor guidance for distribution-specific package names and backported fixes.
  • Prioritize internet-facing mail workflows and administrative automation using net-imap.

Validation and detection

  • Inventory Ruby dependencies for net-imap and compare versions with affected ranges.
  • Review Gemfile.lock, package manifests, and vendor package advisories for patched builds.
  • Trace IMAP command call sites for Symbol arguments derived from external input.
  • Confirm deployments run patched application images or operating-system packages.
  • Run regression tests covering IMAP workflows after dependency or package updates.
Prepared
Confidence
high
Sources
10

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.

cwe · medium confidence lookup

CWE-77: Command execution behavior lookup

Command injection weaknesses can lead defenders to review execution techniques and command interpreter telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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cwe · low confidence lookup

CWE-93: Exact CWE lookup

Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

Execution behavior lookup

The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2026-42258 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.1 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
25Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: noTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.1CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:N2.84.2redhat-SADP
5.8CVSS 4.0MediumCVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N——GitHub_M

Vulnerability scoring details

Base CVSS 4.0 score

5.8Medium
CVSS 4.0 vector shape for CVE-2026-42258Attack VectorAttack ComplexityAttack RequirementsPrivileges RequiredUser InteractionVS ConfidentialityVS IntegrityVS AvailabilitySS ConfidentialitySS IntegritySS Availability

Vector: CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:P/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Attack Requirements
NonePresent
Privileges Required
NoneLowHigh
User Interaction
NonePassiveActive
VS Confidentiality
HighLowNone
VS Integrity
HighLowNone
VS Availability
HighLowNone
SS Confidentiality
HighLowNone
SS Integrity
HighLowNone
SS Availability
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPruby/net-imap: ruby: Net::IMAP: IMAP Command Injection via Symbol Arguments
other:Red Hat severity ratingcvssV3_1
  • 2026-05-09T20:01:01.698Z: Reported to Red Hat.
  • 2026-05-09T19:40:49.405Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
rubynet-imap< 0.4.24, >= 0.5.0, < 0.5.14, >= 0.6.0, < 0.6.4Listed
Weakness

CWE details

CWE-77CWE-93

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-77 · source CWE mapping

Improper Neutralization of Special Elements used in a Command ('Command Injection')

Improper Neutralization of Special Elements used in a Command ('Command Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs
CWE-93 · source CWE mapping

Improper Neutralization of CRLF Sequences ('CRLF Injection')

Improper Neutralization of CRLF Sequences ('CRLF Injection') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

Open CWE intelligenceSame-CWE CVEs