High severity · published May 9, 2026
CVE-2026-42245
net-imap: Quadratic complexity when reading response literals
7.5
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 35% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NE
net-imap · ruby
< 0.4.24; >= 0.5.0, < 0.5.14; >= 0.6.0, < 0.6.4 · source: vendor
NE
Net::imap · Ruby-lang
before 0.4.24; 0.5.0 before 0.5.14; 0.6.0 before 0.6.4 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-42245
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-42245
Patch
https://github.com/ruby/net-imap/commit/6091f7d6b1f3514cafbfe39c76f2b5d73de3ca96
Patch
https://github.com/ruby/net-imap/commit/88d95231fc8afef11c1f074453f7d75b68c9dfda
Patch
https://github.com/ruby/net-imap/commit/de685f91a4a4cc75eb80da898c2bf8af08d34819
Release Notes
https://github.com/ruby/net-imap/releases/tag/v0.4.24
Release Notes
https://github.com/ruby/net-imap/releases/tag/v0.5.14
Release Notes
https://github.com/ruby/net-imap/releases/tag/v0.6.4
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