{"id":"CVE-2026-42256","state":"PUBLISHED","title":"net-imap: Denial of service via high iteration count for `SCRAM-*` authentication","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.","publishedAt":"2026-05-09T19:38:33.106Z","updatedAt":"2026-05-11T17:04:42.562Z","severity":{"score":6,"label":"Medium","version":"4.0","vector":"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","source":"GitHub_M"},"assigner":"GitHub_M","products":["ruby net-imap"],"affected":[{"vendor":"ruby","product":"net-imap","versions":[{"version":">= 0.4.0, < 0.4.24","status":"affected"},{"version":">= 0.5.0, < 0.5.14","status":"affected"},{"version":">= 0.6.0, < 0.6.4","status":"affected"}]}],"references":["https://github.com/ruby/net-imap/security/advisories/GHSA-87pf-fpwv-p7m7","https://github.com/ruby/net-imap/commit/158d0b505074397cdb5ceb58935e42dd2bcfa612","https://github.com/ruby/net-imap/commit/808001bc45c06f7297a7e96d341279e041a7f7f4","https://github.com/ruby/net-imap/commit/99f59eab6064955a23debd95410263ad144df758","https://github.com/ruby/net-imap/releases/tag/v0.4.24","https://github.com/ruby/net-imap/releases/tag/v0.5.14","https://github.com/ruby/net-imap/releases/tag/v0.6.4"],"weaknesses":["CWE-1322","CWE-770"],"ingestedAt":"2026-10-29T20:11:57.932Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/42xxx/CVE-2026-42256.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-42256","state":"PUBLISHED","datePublished":"2026-05-09T19:38:33.106Z","dateUpdated":"2026-05-11T17:04:42.562Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-04-26T11:53:27.704Z"},"containers":{"cna":{"title":"net-imap: Denial of service via high iteration count for `SCRAM-*` authentication","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"ruby","product":"net-imap","versions":[{"version":">= 0.4.0, < 0.4.24","status":"affected"},{"version":">= 0.5.0, < 0.5.14","status":"affected"},{"version":">= 0.6.0, < 0.6.4","status":"affected"}]}],"references":[{"url":"https://github.com/ruby/net-imap/security/advisories/GHSA-87pf-fpwv-p7m7","name":"https://github.com/ruby/net-imap/security/advisories/GHSA-87pf-fpwv-p7m7","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/ruby/net-imap/commit/158d0b505074397cdb5ceb58935e42dd2bcfa612","name":"https://github.com/ruby/net-imap/commit/158d0b505074397cdb5ceb58935e42dd2bcfa612","tags":["x_refsource_MISC"]},{"url":"https://github.com/ruby/net-imap/commit/808001bc45c06f7297a7e96d341279e041a7f7f4","name":"https://github.com/ruby/net-imap/commit/808001bc45c06f7297a7e96d341279e041a7f7f4","tags":["x_refsource_MISC"]},{"url":"https://github.com/ruby/net-imap/commit/99f59eab6064955a23debd95410263ad144df758","name":"https://github.com/ruby/net-imap/commit/99f59eab6064955a23debd95410263ad144df758","tags":["x_refsource_MISC"]},{"url":"https://github.com/ruby/net-imap/releases/tag/v0.4.24","name":"https://github.com/ruby/net-imap/releases/tag/v0.4.24","tags":["x_refsource_MISC"]},{"url":"https://github.com/ruby/net-imap/releases/tag/v0.5.14","name":"https://github.com/ruby/net-imap/releases/tag/v0.5.14","tags":["x_refsource_MISC"]},{"url":"https://github.com/ruby/net-imap/releases/tag/v0.6.4","name":"https://github.com/ruby/net-imap/releases/tag/v0.6.4","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV4_0":{"attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"PRESENT","privilegesRequired":"NONE","userInteraction":"PASSIVE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":6,"baseSeverity":"MEDIUM","vectorString":"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","version":"4.0"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-1322","lang":"en","description":"CWE-1322: Use of Blocking Code in Single-threaded, Non-blocking Context","type":"CWE"}]},{"descriptions":[{"cweId":"CWE-770","lang":"en","description":"CWE-770: Allocation of Resources Without Limits or Throttling","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-05-09T19:38:33.106Z"},"source":{"advisory":"GHSA-87pf-fpwv-p7m7","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-05-11T17:04:26.784816Z","id":"CVE-2026-42256","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-05-11T17:04:42.562Z"}}]}}}