UBUNTU-CVE-2026-54905 (CVE-2026-54905)
Vulnerability from osv_ubuntu – Published: 2026-06-24 17:17 – Updated: 2026-06-29 11:36 – Source website
VLAI
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.
Severity
5.5 (Medium)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "ruby-concurrent",
"binary_version": "1.0.0-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "ruby-concurrent",
"purl": "pkg:deb/ubuntu/ruby-concurrent@1.0.0-1?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.0.0-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "ruby-concurrent",
"binary_version": "1.0.5-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "ruby-concurrent",
"purl": "pkg:deb/ubuntu/ruby-concurrent@1.0.5-1?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.0.5-1"
]
},
{
"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"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "ruby-concurrent",
"purl": "pkg:deb/ubuntu/ruby-concurrent@1.1.6+dfsg-3?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"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-4"
},
{
"binary_name": "ruby-concurrent-ext",
"binary_version": "1.1.6+dfsg-4"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "ruby-concurrent",
"purl": "pkg:deb/ubuntu/ruby-concurrent@1.1.6+dfsg-4?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"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": "1.2.3-2build1"
},
{
"binary_name": "ruby-concurrent-ext",
"binary_version": "1.2.3-2build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "ruby-concurrent",
"purl": "pkg:deb/ubuntu/ruby-concurrent@1.2.3-2build1?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.1.6+dfsg-5build2",
"1.1.6+dfsg-5build3",
"1.2.3-2build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "ruby-concurrent",
"binary_version": "1.3.4-1"
},
{
"binary_name": "ruby-concurrent-ext",
"binary_version": "1.3.4-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:25.10",
"name": "ruby-concurrent",
"purl": "pkg:deb/ubuntu/ruby-concurrent@1.3.4-1?arch=source\u0026distro=questing"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.3.4-1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "ruby-concurrent",
"binary_version": "1.3.6-1"
},
{
"binary_name": "ruby-concurrent-ext",
"binary_version": "1.3.6-1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "ruby-concurrent",
"purl": "pkg:deb/ubuntu/ruby-concurrent@1.3.6-1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.3.4-1",
"1.3.6-1"
]
}
],
"aliases": [],
"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\u0027s 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.",
"id": "UBUNTU-CVE-2026-54905",
"modified": "2026-06-29T11:36:36Z",
"published": "2026-06-24T17:17:00Z",
"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"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"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_V4"
},
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-54905"
]
}
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