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CVE-2026-42246VulnerabilityPublished Updated

Red Hat Security Advisory: ruby security update

Affects Red Hat rubySource GCVE Database

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Authoritative record:CVE-2026-42246· High 7.6

Not known to be exploited · CVSS 7.6 High : upgrade the Red Hat redhat/ruby package to 9.8 soon.

Data as of 12 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 9.8
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 13 Nov 2026.

What to do

Upgrade the Red Hat redhat/ruby package to 9.8.

Affected software

ProductAffectedFixed in
Red Hatredhat/rubypkg:rpm/redhat/rubyOther threatsAffected
  • =9.8
  • <9.8
Fixed in
  • 9.8

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available in net-imap versions 0.3.10, 0.4.24, 0.5.14, and 0.6.4 and corresponding patched Ruby packages from Red Hat. Users should apply these updates promptly. As a temporary workaround, users are strongly encouraged to switch from explicit TLS upgrading mechanisms (STARTTLS on port 143) to implicit TLS connections (IMAPS on port 993), which are not vulnerable to this attack vector. This mitigation bypasses the vulnerable STARTTLS negotiation entirely.

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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