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VulnerabilityPublished Updated

CVE-2026-42246: ruby net-imap · Missing Report of Error Condition

Affects ruby net-imapSource CVE Database V5

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Not known to be exploited · CVSS 7.6 High · fixed in 0.6.4 : patch ruby net-imap soon.

Data as of 10 Nov 2026, 23:24 UTC

CVSS 4.0 base score
7.6High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 24% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.6.4, 0.5.14, 0.4.24 +1
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 9 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 10 Nov 2026.

What to do

Upgrade ruby net-imap to 0.6.4, 0.5.14, 0.4.24 or 0.3.10.

Affected software

ProductAffectedFixed in
rubynet-imapAffected
  • >=0.6.0 <0.6.4
Fixed in
  • 0.6.4
rubynet-imapAffected
  • >=0.5.0 <0.5.14
Fixed in
  • 0.5.14
rubynet-imapAffected
  • >=0.4.0 <0.4.24
Fixed in
  • 0.4.24
rubynet-imapAffected
  • <0.3.10
Fixed in
  • 0.3.10

AI-suggested

A fix is available in net-imap versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4 and later. Users should upgrade to these patched versions to remediate the vulnerability. As a temporary workaround, it is strongly recommended to avoid using STARTTLS on port 143 and instead use implicit TLS connections (IMAPS) on port 993, which are not vulnerable to this attack vector. Red Hat has released security updates for affected Ruby packages in Red Hat Enterprise Linux 7 Extended Lifecycle Support. Users should apply these updates promptly.

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.

References

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