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CVE-2026-42246

net-imap vulnerable to STARTTLS stripping via invalid response timing

Published: May 9, 2026Updated: May 18, 2026 Sources: CVE List NVDCWE-392
NVD MITRE
7.4CVSSHIGH
EPSS Score
0.4%
Top 66.4%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

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.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None
Open in CVSS calculator →

Weaknesses

CWE-392CWE-393CWE-636CWE-754CWE-841

Affected Products

net\ruby-lang
Library
OSS Libraries / generic-library
net-imapruby
Library
OSS Libraries / rubygems
ruby-langoss-projectOSS Librariesaka ruby, rexml
rubyoss-projectJPOSS Libraries

Exploitability

Official Patch Available
Workaround Available

References

https://github.com/ruby/net-imap/commit/0ede4c40b1523dfeaf95777b2678e54cc0fd9618
github.com
https://github.com/ruby/net-imap/commit/24a4e770b43230286a05aa2a9746cdbb3eb8485e
github.com
https://github.com/ruby/net-imap/commit/97e2488fb5401a1783bddd959dde007d9fbce42c
github.com
and 5 more references View all →

Timeline

Published
May 9, 2026
Last Updated
May 18, 2026

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