{"id":"UBUNTU-CVE-2026-54905","details":"concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::ReentrantReadWriteLock can incorrectly grant a write lock after one thread acquires the read lock 32,768 times. The lock stores a thread's local read and write hold counts in one integer. The low 15 bits are used for the read hold count, and bit 15 is used as WRITE_LOCK_HELD. After 32,768 reentrant read acquisitions, the local read count crosses into the write-lock bit. try_write_lock then treats the thread as already holding a write lock and returns true without setting the global RUNNING_WRITER bit. This breaks the core mutual-exclusion guarantee: the caller is told it has a write lock, but other threads can still hold or acquire read locks at the same time. This vulnerability is fixed in 1.3.7.","modified":"2026-06-29T13:55:06.109746394Z","published":"2026-06-24T17:17:00Z","upstream":["CVE-2026-54905"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-54905"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-54905"},{"type":"REPORT","url":"https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp"}],"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_name":"ruby-concurrent","binary_version":"1.0.0-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-54905.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-2026-54905.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_version":"1.1.6+dfsg-3","binary_name":"ruby-concurrent"},{"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-2026-54905.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_name":"ruby-concurrent","binary_version":"1.1.6+dfsg-4"},{"binary_name":"ruby-concurrent-ext","binary_version":"1.1.6+dfsg-4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-54905.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_name":"ruby-concurrent","binary_version":"1.2.3-2build1"},{"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-2026-54905.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-2026-54905.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_version":"1.3.6-1","binary_name":"ruby-concurrent"},{"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-2026-54905.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N"},{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"},{"type":"Ubuntu","score":"medium"}]}