LiveActive security incident?Get immediate response
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
Discuss exposureBack to CVEs
Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Affected Ruby applications may let attacker-influenced Symbol values inject unintended IMAP commands. Successful exploitation could alter mailbox or server-side IMAP state, with limited information exposure also possible. Risk depends on whether untrusted data reaches net-imap command arguments; merely installing the package does not establish exploitability.

Executive priority

Prioritize remediation for externally reachable or automated mail-processing systems where untrusted input can influence IMAP operations. Patch those systems promptly because integrity impact is rated high. Other installations should remain scheduled for upgrade, but validate reachability and data flow before treating every net-imap deployment as directly exploitable.

Technical view

CVE-2026-42258 is a CRLF and IMAP command-injection flaw in Ruby net-imap Symbol argument handling. It affects versions before 0.4.24, 0.5.14, and 0.6.4 in their respective release lines. The supplied CVSS 3.1 score is 7.1: network-reachable, low complexity, no privileges, user interaction required, with high integrity impact.

Likely exposure

Exposure requires an affected net-imap version and an application path that converts or accepts attacker-influenced values as Symbols passed into IMAP commands. Prioritize internet-facing mail workflows, automated mailbox processors, and services accepting external message or request data. The bundle identifies no CPEs, so asset discovery should use dependency inventories and lockfiles.

Exploitation context

The bundle does not report active exploitation, and the CVE is not listed as KEV. The CVSS vector indicates user interaction is required, but the supplied evidence does not define that interaction or identify specific vulnerable application flows. Treat exploitability as application-dependent until data flow into net-imap Symbol arguments is confirmed.

Researcher notes

The reported weakness maps to CWE-77 and CWE-93. The source bundle establishes vulnerable version ranges and fixed releases, but does not enumerate affected methods, required application transformations, observed attacks, or public proof-of-concept activity. Researchers should distinguish dependency presence from a reachable Symbol-input path and avoid inferring operating-system command execution from IMAP command injection.

Mitigation direction

  • Upgrade net-imap 0.4.x to 0.4.24 or later.
  • Upgrade net-imap 0.5.x to 0.5.14 or later.
  • Upgrade net-imap 0.6.x to 0.6.4 or later.
  • Apply applicable Red Hat security updates for vendor-managed packages.
  • Prevent untrusted values from becoming Symbols used as IMAP command arguments.

Validation and detection

  • Inventory deployed net-imap versions using dependency manifests, lockfiles, and runtime package data.
  • Confirm every deployed version meets its release line's patched minimum.
  • Review IMAP call paths for externally influenced values converted to Symbols.
  • Run defensive regression tests confirming malformed inputs cannot create additional IMAP commands.
  • Verify updated deployments, including containers and background workers, use the resolved patched package.
Prepared
Confidence
high
Sources
6

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.

Open ATT&CK lookup
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.

Open ATT&CK lookup
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.

Open ATT&CK lookup
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.

Open ATT&CK lookup
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
28Source 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