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.

Attack Vector Network

Attack Complexity Low

Privileges Required None

Attack Requirements Present

User Interaction Passive

Vulnerable System Confidentiality Impact High

Vulnerable System Integrity Impact High

Vulnerable System Availability Impact None

Subsequent System Confidentiality Impact None

Subsequent System Integrity Impact None

Subsequent System Availability Impact None

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions
ruby net-imap affected
Version Status Constraints
< 0.3.10 affected —
>= 0.4.0, < 0.4.24 affected —
>= 0.5.0, < 0.5.14 affected —
>= 0.6.0, < 0.6.4 affected —

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Project Subscriptions

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-vcgp-9326-pqcp net-imap vulnerable to STARTTLS stripping via invalid response timing
Fixes

Solution

No solution given by the vendor.

Workaround

No workaround given by the vendor.

References
Link Providers
https://github.com/ruby/net-imap/commit/0ede4c40b1523dfeaf95777b2678e54cc0fd9618 cve-icon cve-icon
https://github.com/ruby/net-imap/commit/24a4e770b43230286a05aa2a9746cdbb3eb8485e cve-icon cve-icon
https://github.com/ruby/net-imap/commit/97e2488fb5401a1783bddd959dde007d9fbce42c cve-icon cve-icon
https://github.com/ruby/net-imap/commit/f79d35bf5833f186e81044c57c843eda30c873da cve-icon cve-icon
https://github.com/ruby/net-imap/releases/tag/v0.3.10 cve-icon cve-icon
https://github.com/ruby/net-imap/releases/tag/v0.4.24 cve-icon cve-icon
https://github.com/ruby/net-imap/releases/tag/v0.5.14 cve-icon cve-icon
https://github.com/ruby/net-imap/security/advisories/GHSA-vcgp-9326-pqcp cve-icon cve-icon
History

Sat, 09 May 2026 20:00:00 +0000

Type Values Removed Values Added
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.
Title net-imap vulnerable to STARTTLS stripping via invalid response timing
Weaknesses CWE-392
CWE-393
CWE-636
CWE-754
CWE-841
References
Metrics cvssV4_0

{'score': 7.6, 'vector': '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'}

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-05-09T19:33:17.880Z

Reserved: 2026-04-25T05:37:12.118Z

Link: CVE-2026-42246

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-05-09T20:16:28.163

Modified: 2026-05-09T20:16:28.163

Link: CVE-2026-42246

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-05-09T21:30:42Z

Weaknesses