Medium severity · published May 9, 2026
CVE-2026-42256
net-imap: Denial of service via high iteration count for `SCRAM-*` authentication
6.5
CVSS
0.3%
EPSS
No
On KEV
Description
Net::IMAP implements Internet Message Access Protocol (IMAP) client functionality in Ruby. From versions 0.4.0 to before 0.4.24, 0.5.0 to before 0.5.14, and 0.6.0 to before 0.6.4, when authenticating a connection with SCRAM-SHA1 or SCRAM-SHA256, a hostile server can perform a computational denial-of-service attack on the client process by sending a big iteration count value. 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:R/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 22% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
NE
net-imap · ruby
>= 0.4.0, < 0.4.24; >= 0.5.0, < 0.5.14; >= 0.6.0, < 0.6.4 · source: vendor
NE
Net::imap · Ruby-lang
0.4.0 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-2026-42256
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-42256
Patch
https://github.com/ruby/net-imap/commit/158d0b505074397cdb5ceb58935e42dd2bcfa612
Patch
https://github.com/ruby/net-imap/commit/808001bc45c06f7297a7e96d341279e041a7f7f4
Patch
https://github.com/ruby/net-imap/commit/99f59eab6064955a23debd95410263ad144df758
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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