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Vulnerability record · CVE-2026-42256 · published 9 May 2026

CVE-2026-42256: Ruby-lang net\ allocation without limits vulnerability

Ruby Lang · Net\

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.

6.0 CVSS 4.0 Medium EPSS 0.52% · top 58.2% CWE-770 · Allocation without limitsCWE-1322 · CWE-1322
6.0CVSS 4.0 base score
0.52%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
7References
24 Jul 2026Last modified by NVD

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: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:

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
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 Patch
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 Release Notes
https://github.com/ruby/net-imap/security/advisories/GHSA-87pf-fpwv-p7m7 MitigationVendor Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-42256), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.