Resource exhaustion in Ruby Net-Imap
CVE-2026-42256
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.005 (42.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 43rd percentile — 42.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.005 · change: +0.002
Affected products
- Ruby Net-Imap — versions >= 0.4.0, < 0.4.24, >= 0.5.0, < 0.5.14, >= 0.6.0, < 0.6.4
- Ruby-Lang Net\ — versions \
- Ruby-Lang Net\:\:imap
Weakness classification (CWE)
References
- github.com/ruby/net-imap/security/advisories/GHSA-87pf-fpwv-p7m7 (Mitigation, Vendor Advisory)
- github.com/ruby/net-imap/commit/158d0b505074397cdb5ceb58935e42dd2bcfa612 (Patch)
- github.com/ruby/net-imap/commit/808001bc45c06f7297a7e96d341279e041a7f7f4 (Patch)
- github.com/ruby/net-imap/commit/99f59eab6064955a23debd95410263ad144df758 (Patch)
- github.com/ruby/net-imap/releases/tag/v0.4.24 (Release Notes)
- github.com/ruby/net-imap/releases/tag/v0.5.14 (Release Notes)
- github.com/ruby/net-imap/releases/tag/v0.6.4 (Release Notes)
Frequently asked questions
- What is CVE-2026-42256?
- CVE-2026-42256 is a medium-severity vulnerability in Ruby Net-Imap, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 6.5/10. Published 2026-05-09.
- How severe is CVE-2026-42256?
- Medium severity. CVSS v3 base score is 6.5 out of 10.