High
net-imap vulnerable to STARTTLS stripping via invalid response timing
Type: advisorySources: OSV
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-42246
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 8 Nov 2026, 01:24 UTC · Revision 1
Source evidence
net-imap vulnerable to STARTTLS stripping via invalid response timing
core-osv · Original sourcePublished 9 May 2026, 19:33 UTC
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.
osv:CVE-2026-42246
Complete source record
{
"id": "a824173953aa9a742d2136821d1f9364a2316ad259d295f71b14b6a4e5fb1b45",
"url": "https://osv.dev/vulnerability/CVE-2026-42246",
"method": "structured",
"payload": {
"kind": "advisory",
"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.",
"evidence": "osv:CVE-2026-42246",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-42246",
"aliases": [
"CVE-2026-42246",
"GHSA-vcgp-9326-pqcp"
],
"metrics": [
{
"type": "CVSS_V4",
"score": "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"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/ruby/net-imap",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "ec89812d3c986d6394d3bc0b93048e704aec6af9"
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{
"introduced": "a9459de2c725563d27943e73a92a61f69ef9b048"
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{
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{
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{
"fixed": "3e490673dca65d0cfeeeb3fbf1fdaa188d6f27c4"
},
{
"fixed": "0ede4c40b1523dfeaf95777b2678e54cc0fd9618"
},
{
"fixed": "97e2488fb5401a1783bddd959dde007d9fbce42c"
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{
"fixed": "f79d35bf5833f186e81044c57c843eda30c873da"
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{
"cpe": "cpe:2.3:a:ruby-lang:net\\:\\:imap:*:*:*:*:*:ruby:*:*",
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{
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"source": "CPE_RANGE"
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{
"cpe": "cpe:2.3:a:ruby-lang:net\\:\\:imap:*:*:*:*:*:ruby:*:*",
"range": [
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{
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{
"cpe": "cpe:2.3:a:ruby-lang:net\\:\\:imap:*:*:*:*:*:ruby:*:*",
"range": [
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{
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],
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{
"cpe": "cpe:2.3:a:ruby-lang:net\\:\\:imap:*:*:*:*:*:ruby:*:*",
"range": [
{
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{
"fixed": "0.6.4"
}
],
"source": "CPE_RANGE"
},
{
"range": [
{
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}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
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"source": "REFERENCES_COMMIT"
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{
"range": [
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"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "f79d35bf5833f186e81044c57c843eda30c873da"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "ec89812d3c986d6394d3bc0b93048e704aec6af9"
}
],
"source": "REFERENCES_TAG",
"original_tag": "v0.3.10"
},
{
"range": [
{
"fixed": "24a4e770b43230286a05aa2a9746cdbb3eb8485e"
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],
"source": "REFERENCES_TAG",
"original_tag": "v0.4.24"
},
{
"range": [
{
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}
],
"source": "REFERENCES_TAG",
"original_tag": "v0.5.14"
}
]
}
}
],
"versions": [
"v0.3.9",
"v0.4.23",
"v0.5.13",
"v0.6.2",
"v0.4.22",
"v0.6.0",
"v0.5.12",
"v0.5.11",
"v0.5.10",
"v0.5.9",
"v0.4.21",
"v0.5.8",
"v0.4.20",
"v0.5.7",
"v0.4.19",
"v0.3.8",
"v0.5.6",
"v0.3.7",
"v0.4.18",
"v0.5.5",
"v0.5.4",
"v0.5.3",
"v0.5.2",
"v0.5.1",
"v0.4.17",
"v0.5.0",
"v0.4.16",
"v0.4.15",
"v0.4.14",
"v0.4.13",
"v0.4.12",
"v0.4.11",
"v0.4.10",
"v0.4.9",
"v0.3.4",
"v0.2.3",
"v0.4.8",
"v0.4.7",
"v0.4.6",
"v0.4.5",
"v0.4.4",
"v0.4.3",
"v0.4.2",
"v0.4.1",
"v0.4.0",
"v0.3.6",
"v0.3.5",
"v0.3.3",
"v0.3.2",
"v0.3.1",
"v0.3.0",
"v0.2.2",
"v0.2.1",
"v0.2.0",
"v0.1.1",
"v0.1.0"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-42246.json"
}
}
],
"modified": "2026-10-28T02:30:52.483504200Z",
"provider": "osv",
"references": [
"https://github.com/ruby/net-imap/releases/tag/v0.3.10",
"https://github.com/ruby/net-imap/releases/tag/v0.4.24",
"https://github.com/ruby/net-imap/releases/tag/v0.5.14",
"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-42246.json",
"https://access.redhat.com/errata/RHSA-2026:33462",
"https://access.redhat.com/errata/RHSA-2026:33512",
"https://access.redhat.com/errata/RHSA-2026:33514",
"https://access.redhat.com/errata/RHSA-2026:33515",
"https://access.redhat.com/errata/RHSA-2026:33540",
"https://access.redhat.com/errata/RHSA-2026:33551",
"https://access.redhat.com/errata/RHSA-2026:33552",
"https://access.redhat.com/errata/RHSA-2026:33565",
"https://access.redhat.com/errata/RHSA-2026:33576",
"https://access.redhat.com/errata/RHSA-2026:33577",
"https://access.redhat.com/errata/RHSA-2026:33630",
"https://access.redhat.com/errata/RHSA-2026:33721",
"https://access.redhat.com/errata/RHSA-2026:34076",
"https://access.redhat.com/errata/RHSA-2026:35834",
"https://access.redhat.com/errata/RHSA-2026:35866",
"https://access.redhat.com/errata/RHSA-2026:35867",
"https://access.redhat.com/errata/RHSA-2026:35895",
"https://access.redhat.com/errata/RHSA-2026:36099",
"https://access.redhat.com/errata/RHSA-2026:37238",
"https://access.redhat.com/errata/RHSA-2026:37397",
"https://access.redhat.com/security/cve/CVE-2026-42246",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42246.json",
"https://github.com/ruby/net-imap/security/advisories/GHSA-vcgp-9326-pqcp",
"https://nvd.nist.gov/vuln/detail/CVE-2026-42246",
"https://bugzilla.redhat.com/show_bug.cgi?id=2468499",
"https://github.com/ruby/net-imap/commit/0ede4c40b1523dfeaf95777b2678e54cc0fd9618",
"https://github.com/ruby/net-imap/commit/24a4e770b43230286a05aa2a9746cdbb3eb8485e",
"https://github.com/ruby/net-imap/commit/97e2488fb5401a1783bddd959dde007d9fbce42c",
"https://github.com/ruby/net-imap/commit/f79d35bf5833f186e81044c57c843eda30c873da"
],
"provider_metadata": {
"cwe_ids": [
"CWE-392",
"CWE-393",
"CWE-636",
"CWE-754",
"CWE-841"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42246.json"
}
},
"related_cves": [
{
"value": "CVE-2026-42246",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 521313,
"published_at": "2026-05-09T19:33:17.88+00:00"
}