CVE-2026-42246 (GCVE-0-2026-42246)
Vulnerability from cvelistv5 – Published: 2026-05-09 19:33 – Updated: 2026-05-09 19:33
VLAI?
Title
net-imap vulnerable to STARTTLS stripping via invalid response timing
Summary
Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4, a man-in-the-middle attacker can cause Net::IMAP#starttls to return "successfully", without starting TLS. This issue has been patched in versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4.
Severity ?
CWE
Assigner
References
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Impacted products
{
"containers": {
"cna": {
"affected": [
{
"product": "net-imap",
"vendor": "ruby",
"versions": [
{
"status": "affected",
"version": "\u003c 0.3.10"
},
{
"status": "affected",
"version": "\u003e= 0.4.0, \u003c 0.4.24"
},
{
"status": "affected",
"version": "\u003e= 0.5.0, \u003c 0.5.14"
},
{
"status": "affected",
"version": "\u003e= 0.6.0, \u003c 0.6.4"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4, a man-in-the-middle attacker can cause Net::IMAP#starttls to return \"successfully\", without starting TLS. This issue has been patched in versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4."
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "NETWORK",
"baseScore": 7.6,
"baseSeverity": "HIGH",
"privilegesRequired": "NONE",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "PASSIVE",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
"version": "4.0",
"vulnAvailabilityImpact": "NONE",
"vulnConfidentialityImpact": "HIGH",
"vulnIntegrityImpact": "HIGH"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-392",
"description": "CWE-392: Missing Report of Error Condition",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-393",
"description": "CWE-393: Return of Wrong Status Code",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-754",
"description": "CWE-754: Improper Check for Unusual or Exceptional Conditions",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-636",
"description": "CWE-636: Not Failing Securely (\u0027Failing Open\u0027)",
"lang": "en",
"type": "CWE"
}
]
},
{
"descriptions": [
{
"cweId": "CWE-841",
"description": "CWE-841: Improper Enforcement of Behavioral Workflow",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-09T19:33:17.880Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/ruby/net-imap/security/advisories/GHSA-vcgp-9326-pqcp",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/ruby/net-imap/security/advisories/GHSA-vcgp-9326-pqcp"
},
{
"name": "https://github.com/ruby/net-imap/commit/0ede4c40b1523dfeaf95777b2678e54cc0fd9618",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/ruby/net-imap/commit/0ede4c40b1523dfeaf95777b2678e54cc0fd9618"
},
{
"name": "https://github.com/ruby/net-imap/commit/24a4e770b43230286a05aa2a9746cdbb3eb8485e",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/ruby/net-imap/commit/24a4e770b43230286a05aa2a9746cdbb3eb8485e"
},
{
"name": "https://github.com/ruby/net-imap/commit/97e2488fb5401a1783bddd959dde007d9fbce42c",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/ruby/net-imap/commit/97e2488fb5401a1783bddd959dde007d9fbce42c"
},
{
"name": "https://github.com/ruby/net-imap/commit/f79d35bf5833f186e81044c57c843eda30c873da",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/ruby/net-imap/commit/f79d35bf5833f186e81044c57c843eda30c873da"
},
{
"name": "https://github.com/ruby/net-imap/releases/tag/v0.3.10",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/ruby/net-imap/releases/tag/v0.3.10"
},
{
"name": "https://github.com/ruby/net-imap/releases/tag/v0.4.24",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/ruby/net-imap/releases/tag/v0.4.24"
},
{
"name": "https://github.com/ruby/net-imap/releases/tag/v0.5.14",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/ruby/net-imap/releases/tag/v0.5.14"
}
],
"source": {
"advisory": "GHSA-vcgp-9326-pqcp",
"discovery": "UNKNOWN"
},
"title": "net-imap vulnerable to STARTTLS stripping via invalid response timing"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-42246",
"datePublished": "2026-05-09T19:33:17.880Z",
"dateReserved": "2026-04-25T05:37:12.118Z",
"dateUpdated": "2026-05-09T19:33:17.880Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2026-42246\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-05-09T20:16:28.163\",\"lastModified\":\"2026-05-09T20:16:28.163\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4, a man-in-the-middle attacker can cause Net::IMAP#starttls to return \\\"successfully\\\", without starting TLS. This issue has been patched in versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4.\"}],\"metrics\":{\"cvssMetricV40\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"4.0\",\"vectorString\":\"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/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\":7.6,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"attackRequirements\":\"PRESENT\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"PASSIVE\",\"vulnConfidentialityImpact\":\"HIGH\",\"vulnIntegrityImpact\":\"HIGH\",\"vulnAvailabilityImpact\":\"NONE\",\"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\"}}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-392\"},{\"lang\":\"en\",\"value\":\"CWE-393\"},{\"lang\":\"en\",\"value\":\"CWE-636\"},{\"lang\":\"en\",\"value\":\"CWE-754\"},{\"lang\":\"en\",\"value\":\"CWE-841\"}]}],\"references\":[{\"url\":\"https://github.com/ruby/net-imap/commit/0ede4c40b1523dfeaf95777b2678e54cc0fd9618\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ruby/net-imap/commit/24a4e770b43230286a05aa2a9746cdbb3eb8485e\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ruby/net-imap/commit/97e2488fb5401a1783bddd959dde007d9fbce42c\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ruby/net-imap/commit/f79d35bf5833f186e81044c57c843eda30c873da\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ruby/net-imap/releases/tag/v0.3.10\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ruby/net-imap/releases/tag/v0.4.24\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ruby/net-imap/releases/tag/v0.5.14\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ruby/net-imap/security/advisories/GHSA-vcgp-9326-pqcp\",\"source\":\"security-advisories@github.com\"}]}}"
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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