CVE-2026-42256

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 6.5 under NVD CVSS v3. EPSS exploit probability: 0.3%, top 78% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
6.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 6.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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 v3
6.5
EG Score
6.5(medium)
EPSS
21.6%
KEV
Not listed

Published

May 9, 2026

Last Modified

May 18, 2026

Advisory Details (7)

Auto-updated May 18, 2026
Patch available. Sources: github.
github Patch Available

Denial of service via high iteration count for `SCRAM-*` authentication · Advisory · ruby/net-imap · GitHub

https://github.com/ruby/net-imap/security/advisories/GHSA-87pf-fpwv-p7m7
generic

Release v0.6.4 · ruby/net-imap · GitHub

https://github.com/ruby/net-imap/releases/tag/v0.6.4
generic

Release v0.5.14 · ruby/net-imap · GitHub

https://github.com/ruby/net-imap/releases/tag/v0.5.14
generic

Release v0.4.24 · ruby/net-imap · GitHub

https://github.com/ruby/net-imap/releases/tag/v0.4.24
generic

🔀 Merge pull request #654 from ruby/scram-maximum_iterations · ruby/net-imap@99f59ea · GitHub

https://github.com/ruby/net-imap/commit/99f59eab6064955a23debd95410263ad144df758
generic

🔀 Merge pull request #656 from ruby/backport/v0.5/scram-maximum_itera… · ruby/net-imap@808001b · GitHub

https://github.com/ruby/net-imap/commit/808001bc45c06f7297a7e96d341279e041a7f7f4
generic

🔀 Merge pull request #655 from ruby/backport/v0.4/scram-maximum_itera… · ruby/net-imap@158d0b5 · GitHub

https://github.com/ruby/net-imap/commit/158d0b505074397cdb5ceb58935e42dd2bcfa612

Vendor Advisories for CVE-2026-42256(4)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(1 across 1 ecosystem)
RubyGems(1)
PackageVulnerable rangeFixed inDependents
net-imap0.4.0 ... 0.4.9.1 (25 versions)0.4.24—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 8× in last 7d / 48× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 16:27 UTCEPSS rescore
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  3. 2026-07-06 02:23 UTCEPSS rescore
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  10. 2026-06-28 14:07 UTCEPSS rescore
  11. 2026-06-28 04:56 UTCEPSS rescore
  12. 2026-06-27 10:31 UTCEG score recompute
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  15. 2026-06-25 13:49 UTCEPSS rescore
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  17. 2026-06-24 14:05 UTCEPSS rescore
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  1. 2026-06-18 17:52 UTCEPSS rescore
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  3. 2026-06-16 17:52 UTCEPSS rescore
  4. 2026-06-16 07:50 UTCEG score recompute
  5. 2026-06-15 17:49 UTCEPSS rescore
  6. 2026-06-14 10:43 UTCEG score recompute
  7. 2026-06-13 23:00 UTCEPSS rescore
  8. 2026-06-13 09:12 UTCEG score recompute
  9. 2026-06-12 23:12 UTCEPSS rescore
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  11. 2026-06-12 01:48 UTCEG score recompute
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  17. 2026-06-09 22:40 UTCEG score recompute
  18. 2026-06-08 20:33 UTCEG score recompute
  19. 2026-06-08 14:17 UTCEPSS rescore
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  21. 2026-06-07 16:21 UTCEG score recompute
  22. 2026-06-07 15:25 UTCEPSS rescore
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  24. 2026-06-06 14:52 UTCEG score recompute
  25. 2026-06-06 13:47 UTCEPSS rescore
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  27. 2026-06-05 22:47 UTCEPSS rescore
  28. 2026-06-05 13:22 UTCEG score recompute
  29. 2026-06-05 06:10 UTCEPSS rescore
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  31. 2026-06-04 13:12 UTCEPSS rescore
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  33. 2026-06-04 11:52 UTCEG score recompute
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  35. 2026-06-02 20:13 UTCEPSS rescore
  36. 2026-06-02 08:52 UTCEG score recompute
  37. 2026-06-01 13:52 UTCEPSS rescore
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  39. 2026-06-01 07:22 UTCEG score recompute
  40. 2026-05-31 22:30 UTCEPSS rescore
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  42. 2026-05-31 00:16 UTCEPSS rescore
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  44. 2026-05-29 13:44 UTCEPSS rescore
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  52. 2026-05-26 13:44 UTCEPSS rescore
  53. 2026-05-26 07:18 UTCEPSS rescore
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  55. 2026-05-23 00:07 UTCEG score recompute
  56. 2026-05-20 22:38 UTCEPSS rescore
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  58. 2026-05-20 13:27 UTCEG score recompute
  59. 2026-05-20 11:22 UTCEPSS rescore
  60. 2026-05-20 11:22 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-42256?
CVE-2026-42256 is a medium vulnerability published on May 9, 2026. 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…
When was CVE-2026-42256 disclosed?
CVE-2026-42256 was first published in the National Vulnerability Database on May 9, 2026, with the most recent update on May 18, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-42256 actively exploited?
CVE-2026-42256 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 21.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-42256?
CVE-2026-42256 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-42256?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-42256, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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