net-imap: Denial of service via high iteration count for `SCRAM-*` authentication

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Summary

CVECVE-2026-42256
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-09 20:16:28 UTC
Updated2026-05-09 20:16:28 UTC
DescriptionNet::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.

Risk And Classification

Primary CVSS: v4.0 6 MEDIUM from [email protected]

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-770 | CWE-1322 | CWE-1322 CWE-1322: Use of Blocking Code in Single-threaded, Non-blocking Context | CWE-770 CWE-770: Allocation of Resources Without Limits or Throttling

VersionSourceTypeScoreSeverityVector
4.0[email protected]Secondary6MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/C...
4.0CNADECLARED6MEDIUMCVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
Present
Privileges Required
None
User Interaction
Passive
Confidentiality
None
Integrity
None
Availability
High
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Ruby Net-imap affected >= 0.4.0, < 0.4.24 Not specified
CNA Ruby Net-imap affected >= 0.5.0, < 0.5.14 Not specified
CNA Ruby Net-imap affected >= 0.6.0, < 0.6.4 Not specified

References

ReferenceSourceLinkTags
github.com/ruby/net-imap/commit/808001bc45c06f7297a7e96d341279e041a7f7f4 [email protected] github.com
github.com/ruby/net-imap/releases/tag/v0.6.4 [email protected] github.com
github.com/ruby/net-imap/releases/tag/v0.5.14 [email protected] github.com
github.com/ruby/net-imap/commit/99f59eab6064955a23debd95410263ad144df758 [email protected] github.com
github.com/ruby/net-imap/releases/tag/v0.4.24 [email protected] github.com
github.com/ruby/net-imap/security/advisories/GHSA-87pf-fpwv-p7m7 [email protected] github.com
github.com/ruby/net-imap/commit/158d0b505074397cdb5ceb58935e42dd2bcfa612 [email protected] github.com
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