{"id":"UBUNTU-CVE-2026-54904","details":"concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::AtomicReference#update can enter a permanent busy retry loop when the current value is Float::NAN. The issue is caused by the interaction between AtomicReference#update, which retries until compare_and_set(old_value, new_value) succeeds; Numeric compare_and_set, which checks old == old_value before attempting the underlying atomic swap.; and Ruby NaN semantics, where Float::NAN == Float::NAN is always false. As a result, once an AtomicReference contains Float::NAN, calling #update repeatedly evaluates the caller's block and never returns. In services that store externally derived numeric values in an AtomicReference, this can cause CPU exhaustion or permanent request/job hangs. This vulnerability is fixed in 1.3.7.","modified":"2026-06-29T13:55:06.189753224Z","published":"2026-06-24T17:17:00Z","upstream":["CVE-2026-54904"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-54904"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-54904"},{"type":"REPORT","url":"https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-h8w8-99g7-qmvj"}],"affected":[{"package":{"name":"ruby-concurrent","ecosystem":"Ubuntu:16.04:LTS","purl":"pkg:deb/ubuntu/ruby-concurrent?arch=source&distro=xenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.0-1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.0.0-1","binary_name":"ruby-concurrent"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-54904.json"}},{"package":{"name":"ruby-concurrent","ecosystem":"Ubuntu:18.04:LTS","purl":"pkg:deb/ubuntu/ruby-concurrent?arch=source&distro=bionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.5-1"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-concurrent","binary_version":"1.0.5-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-54904.json"}},{"package":{"name":"ruby-concurrent","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/ruby-concurrent?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.0.5-3","1.0.5-4","1.1.6+dfsg-2","1.1.6+dfsg-3"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-concurrent","binary_version":"1.1.6+dfsg-3"},{"binary_name":"ruby-concurrent-ext","binary_version":"1.1.6+dfsg-3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-54904.json"}},{"package":{"name":"ruby-concurrent","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/ruby-concurrent?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.1.6+dfsg-3","1.1.6+dfsg-3build1","1.1.6+dfsg-4"],"ecosystem_specific":{"binaries":[{"binary_version":"1.1.6+dfsg-4","binary_name":"ruby-concurrent"},{"binary_version":"1.1.6+dfsg-4","binary_name":"ruby-concurrent-ext"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-54904.json"}},{"package":{"name":"ruby-concurrent","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/ruby-concurrent?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.1.6+dfsg-5build2","1.1.6+dfsg-5build3","1.2.3-2build1"],"ecosystem_specific":{"binaries":[{"binary_version":"1.2.3-2build1","binary_name":"ruby-concurrent"},{"binary_name":"ruby-concurrent-ext","binary_version":"1.2.3-2build1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-54904.json"}},{"package":{"name":"ruby-concurrent","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/ruby-concurrent?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.3.4-1"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-concurrent","binary_version":"1.3.4-1"},{"binary_name":"ruby-concurrent-ext","binary_version":"1.3.4-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-54904.json"}},{"package":{"name":"ruby-concurrent","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/ruby-concurrent?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.3.4-1","1.3.6-1"],"ecosystem_specific":{"binaries":[{"binary_name":"ruby-concurrent","binary_version":"1.3.6-1"},{"binary_name":"ruby-concurrent-ext","binary_version":"1.3.6-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-54904.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},{"type":"Ubuntu","score":"medium"}]}