What’s Vulnerable › Vulnerabilities

CVE-2026-42245: net-imap: Quadratic complexity when reading response literals

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-05-09 · updated 2026-07-24
• Weakness: CWE-407

Description

Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. Prior to versions 0.4.24, 0.5.14, and 0.6.4, Net::IMAP::ResponseReader has quadratic time complexity when reading large responses containing many string literals. A hostile server can send responses which are crafted to exhaust the client's CPU for a denial of service attack. This issue has been patched in versions 0.4.24, 0.5.14, and 0.6.4.

Affected products

• ruby-lang Net::Imap: before 0.4.24; from 0.5.0 before 0.5.14; from 0.6.0 before 0.6.4 — fixed in 0.4.24, 0.5.14, 0.6.4

How to fix

Upgrade to a fixed version: ruby-lang Net::Imap 0.4.24, 0.5.14, 0.6.4. Check the vendor advisory for mitigations.

References

• https://github.com/ruby/net-imap/commit/6091f7d6b1f3514cafbfe39c76f2b5d73de3ca96
• https://github.com/ruby/net-imap/commit/88d95231fc8afef11c1f074453f7d75b68c9dfda
• https://github.com/ruby/net-imap/commit/de685f91a4a4cc75eb80da898c2bf8af08d34819
• https://github.com/ruby/net-imap/releases/tag/v0.4.24
• https://github.com/ruby/net-imap/releases/tag/v0.5.14
• https://github.com/ruby/net-imap/releases/tag/v0.6.4
• https://github.com/ruby/net-imap/security/advisories/GHSA-q2mw-fvj9-vvcw

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