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© 2026 FAUCET Technologies LLC. All rights reserved.

CVE-2026-42246

33
FAUCET Score

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.

First published: May 9, 2026Last modified: May 12, 2026

Impacted Technologies

VendorProductVersion(s)CPE
< 0.3.10CPE matchmatch criteria
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*
>= 0.4.0, < 0.4.24CPE matchmatch criteria
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*
>= 0.5.0, < 0.5.14CPE matchmatch criteria
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*
>= 0.6.0, < 0.6.4CPE matchmatch criteria
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:*

CVSS Data

CVSS version used by this source: 4.0

7.6HIGH

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

Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
PRESENT
Privileges Required
NONE
User Interaction
PASSIVE
VS Confidentiality
HIGH
VS Integrity
HIGH
VS Availability
NONE
SS Confidentiality
NONE
SS Integrity
NONE
SS Availability
NONE
Exploit Maturity
NOT_DEFINED
CvssVersion
4.0

Exploit Intelligence

EPSS Score
0.31%
Probability of exploitation in next 30 days
EPSS Percentile
23.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0031 is in the 4th percentile among its peer group of 8,918 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (7)

github_advisorypatch availablevia nvd_reference
View patch
rubygemspatch availablevia ghsa
Product: net-imapFixed in: 0.5.14
rubygemspatch availablevia ghsa
Product: net-imapFixed in: 0.4.24
rubygemspatch availablevia ghsa
Product: net-imapFixed in: 0.6.4
rubygemspatch availablevia ghsa
Product: net-imapFixed in: 0.3.10
ubuntupatch availablevia ubuntu_usn
Product: ruby2.5 (bionic)Fixed in: 2.5.1-1ubuntu1.16+esm8
ubuntupatch availablevia ubuntu_usn
Product: ruby2.3 (xenial)Fixed in: 2.3.1-2~ubuntu16.04.16+esm14

Vendor Advisories (3)

ubuntuUSN-8431-1

Ruby vulnerabilities

Jun 15, 2026
microsoft2026-May/CVE-2026-42246Important

net-imap vulnerable to STARTTLS stripping via invalid response timing

May 7, 2026
rubygemsGHSA-vcgp-9326-pqcphigh

net-imap vulnerable to STARTTLS stripping via invalid response timing

May 4, 2026

References

access.redhat.com / errata/RHSA-2026:33462
access.redhat.com / errata/RHSA-2026:33512
access.redhat.com / errata/RHSA-2026:33514
access.redhat.com / errata/RHSA-2026:33515
access.redhat.com / errata/RHSA-2026:33540
access.redhat.com / errata/RHSA-2026:33551
access.redhat.com / errata/RHSA-2026:33552
access.redhat.com / errata/RHSA-2026:33565
access.redhat.com / errata/RHSA-2026:33576
access.redhat.com / errata/RHSA-2026:33577
access.redhat.com / errata/RHSA-2026:33630
access.redhat.com / errata/RHSA-2026:33721
access.redhat.com / errata/RHSA-2026:34076
access.redhat.com / errata/RHSA-2026:35834
access.redhat.com / errata/RHSA-2026:35866
access.redhat.com / errata/RHSA-2026:35867
access.redhat.com / errata/RHSA-2026:35895
access.redhat.com / errata/RHSA-2026:36099
access.redhat.com / errata/RHSA-2026:37238
access.redhat.com / errata/RHSA-2026:37397
access.redhat.com / security/cve/CVE-2026-42246
bugzilla.redhat.com / show_bug.cgi
security.access.redhat.com / data/csaf/v2/vex/2026/cve-2026-42246.json
github.com / ruby/net-imap/commit/0ede4c40b1523dfeaf95777b2678e54cc0fd9618
Patch
github.com / ruby/net-imap/commit/24a4e770b43230286a05aa2a9746cdbb3eb8485e
Patch
github.com / ruby/net-imap/commit/97e2488fb5401a1783bddd959dde007d9fbce42c
Patch
github.com / ruby/net-imap/commit/f79d35bf5833f186e81044c57c843eda30c873da
Patch
github.com / ruby/net-imap/releases/tag/v0.3.10
Release Notes
github.com / ruby/net-imap/releases/tag/v0.4.24
Release Notes
github.com / ruby/net-imap/releases/tag/v0.5.14
Release Notes
github.com / ruby/net-imap/security/advisories/GHSA-vcgp-9326-pqcp
MitigationVendor Advisory