CVE-2026-54905 (GCVE-0-2026-54905)
Vulnerability from cvelistv5 – Published: 2026-06-24 15:42 – Updated: 2026-06-24 16:41
VLAI
EPSS
VEX
Title
concurrent-ruby: `ReentrantReadWriteLock` read-count overflow grants a write lock without exclusivity
Summary
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
SSVC
Exploitation: poc
Automatable: no
Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-24 16:41 UTC
CWE
- CWE-128 - Wrap-around Error
Assigner
References
1 reference
| URL | Tags |
|---|---|
| https://github.com/ruby-concurrency/concurrent-ru… | x_refsource_CONFIRM |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| ruby-concurrency | concurrent-ruby |
Affected:
< 1.3.7
|
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-54905",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-06-24T16:41:31.221708Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-06-24T16:41:34.224Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"exploit"
],
"url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "concurrent-ruby",
"vendor": "ruby-concurrency",
"versions": [
{
"status": "affected",
"version": "\u003c 1.3.7"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"baseScore": 2,
"baseSeverity": "LOW",
"privilegesRequired": "LOW",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"vectorString": "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",
"version": "4.0",
"vulnAvailabilityImpact": "LOW",
"vulnConfidentialityImpact": "LOW",
"vulnIntegrityImpact": "LOW"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-128",
"description": "CWE-128: Wrap-around Error",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-06-24T15:42:44.257Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp"
}
],
"source": {
"advisory": "GHSA-wv3x-4vxv-whpp",
"discovery": "UNKNOWN"
},
"title": "concurrent-ruby: `ReentrantReadWriteLock` read-count overflow grants a write lock without exclusivity"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-54905",
"datePublished": "2026-06-24T15:42:44.257Z",
"dateReserved": "2026-06-16T13:49:33.556Z",
"dateUpdated": "2026-06-24T16:41:34.224Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-54905",
"date": "2026-09-18",
"epss": "0.00153",
"percentile": "0.04829"
},
"microsoft_vex": {
"current_release_date": "2026-06-30T15:41:39.000Z",
"cve": "CVE-2026-54905",
"id": "msrc_CVE-2026-54905",
"initial_release_date": "2026-06-02T00:00:00.000Z",
"product_status:fixed": "1",
"product_status:known_affected": "1",
"source": "Microsoft CSAF VEX",
"status": "final",
"title": "concurrent-ruby: `ReentrantReadWriteLock` read-count overflow grants a write lock without exclusivity",
"url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-54905.json",
"version": "3"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"product": "concurrent-ruby",
"vendor": "ruby-concurrency",
"versions": [
{
"status": "affected",
"version": "\u003c 1.3.7"
}
]
}
],
"source": "security-advisories@github.com"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:rubyconcurrency:concurrent_ruby:*:*:*:*:*:ruby:*:*",
"matchCriteriaId": "4BBFFB42-BEF4-4DF8-BAB8-4B728A8CA930",
"versionEndExcluding": "1.3.7",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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": "CVE-2026-54905",
"lastModified": "2026-06-26T20:01:00.517",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "NONE",
"baseScore": 5.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 3.6,
"source": "nvd@nist.gov",
"type": "Primary"
}
],
"cvssMetricV40": [
{
"cvssData": {
"Automatable": "NOT_DEFINED",
"Recovery": "NOT_DEFINED",
"Safety": "NOT_DEFINED",
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"availabilityRequirement": "NOT_DEFINED",
"baseScore": 2.0,
"baseSeverity": "LOW",
"confidentialityRequirement": "NOT_DEFINED",
"exploitMaturity": "NOT_DEFINED",
"integrityRequirement": "NOT_DEFINED",
"modifiedAttackComplexity": "NOT_DEFINED",
"modifiedAttackRequirements": "NOT_DEFINED",
"modifiedAttackVector": "NOT_DEFINED",
"modifiedPrivilegesRequired": "NOT_DEFINED",
"modifiedSubAvailabilityImpact": "NOT_DEFINED",
"modifiedSubConfidentialityImpact": "NOT_DEFINED",
"modifiedSubIntegrityImpact": "NOT_DEFINED",
"modifiedUserInteraction": "NOT_DEFINED",
"modifiedVulnAvailabilityImpact": "NOT_DEFINED",
"modifiedVulnConfidentialityImpact": "NOT_DEFINED",
"modifiedVulnIntegrityImpact": "NOT_DEFINED",
"privilegesRequired": "LOW",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"valueDensity": "NOT_DEFINED",
"vectorString": "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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
"version": "4.0",
"vulnAvailabilityImpact": "LOW",
"vulnConfidentialityImpact": "LOW",
"vulnIntegrityImpact": "LOW",
"vulnerabilityResponseEffort": "NOT_DEFINED"
},
"source": "security-advisories@github.com",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-54905",
"options": [
{
"exploitation": "poc"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-06-24T16:41:31.221708Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-06-24T17:17:29.403",
"references": [
{
"source": "security-advisories@github.com",
"tags": [
"Third Party Advisory"
],
"url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp"
},
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"tags": [
"Third Party Advisory"
],
"url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp"
}
],
"sourceIdentifier": "security-advisories@github.com",
"vulnStatus": "Analyzed",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-128"
}
],
"source": "security-advisories@github.com",
"type": "Primary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Low",
"current_release_date": "2026-06-26T21:55:37+00:00",
"cve": "CVE-2026-54905",
"id": "CVE-2026-54905",
"initial_release_date": "2026-06-24T15:42:44.257000+00:00",
"product_status:known_affected": "20",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "concurrent-ruby: Concurrent-ruby: Incorrect write lock granting leading to broken mutual exclusion",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-54905.json",
"version": "3"
},
"suse_vex": {
"aggregate_severity": "moderate",
"current_release_date": "2026-08-31T16:39:12Z",
"cve": "CVE-2026-54905",
"id": "CVE-2026-54905",
"initial_release_date": "2026-06-23T02:19:44Z",
"product_status:known_affected": "86",
"product_status:known_not_affected": "5",
"source": "SUSE CSAF VEX",
"status": "interim",
"title": "SUSE CVE CVE-2026-54905",
"url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-54905.json",
"version": "4"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-54905",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "no"
},
{
"Technical Impact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-06-24T16:41:31.221708Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-06-24T16:39:54.356Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"exploit"
],
"url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "concurrent-ruby",
"vendor": "ruby-concurrency",
"versions": [
{
"status": "affected",
"version": "\u003c 1.3.7"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "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."
}
],
"metrics": [
{
"cvssV4_0": {
"attackComplexity": "LOW",
"attackRequirements": "PRESENT",
"attackVector": "LOCAL",
"baseScore": 2,
"baseSeverity": "LOW",
"privilegesRequired": "LOW",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "NONE",
"vectorString": "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",
"version": "4.0",
"vulnAvailabilityImpact": "LOW",
"vulnConfidentialityImpact": "LOW",
"vulnIntegrityImpact": "LOW"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-128",
"description": "CWE-128: Wrap-around Error",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-06-24T15:42:44.257Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp"
}
],
"source": {
"advisory": "GHSA-wv3x-4vxv-whpp",
"discovery": "UNKNOWN"
},
"title": "concurrent-ruby: `ReentrantReadWriteLock` read-count overflow grants a write lock without exclusivity"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-54905",
"datePublished": "2026-06-24T15:42:44.257Z",
"dateReserved": "2026-06-16T13:49:33.556Z",
"dateUpdated": "2026-06-24T16:41:34.224Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
Loading…