net-imap vulnerable to STARTTLS stripping via invalid response timing (ruby net-imap)

CVE-2026-42246

HIGH 7.6

At a glance

Source: NVD
EPSS: EPSS 0.31 % · percentile 24 (2026-10-31)
State: PUBLISHED
Published: 2026-05-09 19:33 UTC
Updated: 2026-08-24 12:06 UTC
Assigner: GitHub_M
NVD status: Modified

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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.

Weaknesses (CWE)

CWE-392 — Missing Report of Error Condition
CWE-393 — Return of Wrong Status Code
CWE-754 — Improper Check for Unusual or Exceptional Conditions
CWE-636 — Not Failing Securely
CWE-841 — Improper Enforcement of Behavioral Workflow
CWE-325 — Missing Cryptographic Step

References

Scores

Version	Score	Vector	Scored by
CVSS 4.0	HIGH 7.6	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	GitHub_M
CVSS 3.1	HIGH 7.4	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N	redhat-SADP
CVSS 4.0	HIGH 7.6	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	NVD · security-advisories@github.com (Secondary)
CVSS 3.1	HIGH 7.4	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N	NVD · nvd@nist.gov (Primary)
CVSS 3.1	HIGH 7.4	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N	NVD · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c (Secondary)

Advisories

GHSA-vcgp-9326-pqcp — net-imap vulnerable to STARTTLS stripping via invalid response timing

European references

ENISA EUVD · EUVD-2026-28924
GCVE · GCVE-0-2026-42246

CERT-FR advisories

CERTFR-2026-AVI-0958 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr

Affected configurations (NVD CPE)

cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:* < 0.3.10
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:* ≥ 0.4.0 < 0.4.24
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:* ≥ 0.5.0 < 0.5.14
cpe:2.3:a:ruby-lang:net\:\:imap:*:*:*:*:*:ruby:*:* ≥ 0.6.0 < 0.6.4

Affected products

Product	Versions
ruby · net-imap	affected < 0.3.10 ; affected >= 0.4.0, < 0.4.24 ; affected >= 0.5.0, < 0.5.14 ; affected >= 0.6.0, < 0.6.4

Sources

Source	Licence
CVE List (CVEProject cvelistV5)	CVE Program Terms of Use
EPSS (FIRST.org)	FIRST — attribution requested
ENISA EUVD	ENISA — reproduction authorised, source acknowledged
CERT-FR (ANSSI)	Licence Ouverte / Etalab 2.0
NVD (NIST) via fkie-cad/nvd-json-data-feeds	Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD

⚠️ net-imap vulnerable to STARTTLS stripping via invalid response timing (ruby net-imap)