GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

CVE-2026-54906 (GCVE-0-2026-54906)

Vulnerability from cvelistv5 – Published: 2026-06-24 15:46 – Updated: 2026-06-24 17:57
VLAI
Title
concurrent-ruby: ReadWriteLock allows wrong-thread write release and stray read-release counter corruption
Summary
concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::ReadWriteLock#release_write_lock does not verify that the calling thread acquired the write lock. Any thread with access to the lock object can release an active write lock held by another thread. A second writer can then enter its critical section while the first writer is still running. Concurrent::ReadWriteLock#release_read_lock also decrements the shared counter even when no read lock is held. Calling it on a fresh lock changes the counter from 0 to -1, after which normal read acquisition raises Concurrent::ResourceLimitError. This is a synchronization correctness issue in the public Concurrent::ReadWriteLock API. This vulnerability is fixed in 1.3.7.
SSVC
Exploitation: poc Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-24 17:56 UTC
CWE
References
Impacted products
Vendor Product Version CPE status
ruby-concurrency concurrent-ruby Affected: < 1.3.7
guessed Create a notification for this product.
Show details on NVD website

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-54906",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-24T17:56:44.670673Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-24T17:57:07.650Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr"
          }
        ],
        "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::ReadWriteLock#release_write_lock does not verify that the calling thread acquired the write lock. Any thread with access to the lock object can release an active write lock held by another thread. A second writer can then enter its critical section while the first writer is still running. Concurrent::ReadWriteLock#release_read_lock also decrements the shared counter even when no read lock is held. Calling it on a fresh lock changes the counter from 0 to -1, after which normal read acquisition raises Concurrent::ResourceLimitError. This is a synchronization correctness issue in the public Concurrent::ReadWriteLock API. This vulnerability is fixed in 1.3.7."
        }
      ],
      "metrics": [
        {
          "cvssV4_0": {
            "attackComplexity": "HIGH",
            "attackRequirements": "NONE",
            "attackVector": "LOCAL",
            "baseScore": 2.1,
            "baseSeverity": "LOW",
            "privilegesRequired": "NONE",
            "subAvailabilityImpact": "NONE",
            "subConfidentialityImpact": "NONE",
            "subIntegrityImpact": "NONE",
            "userInteraction": "NONE",
            "vectorString": "CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N",
            "version": "4.0",
            "vulnAvailabilityImpact": "LOW",
            "vulnConfidentialityImpact": "NONE",
            "vulnIntegrityImpact": "LOW"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-414",
              "description": "CWE-414: Missing Lock Check",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-667",
              "description": "CWE-667: Improper Locking",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-06-24T15:46:01.116Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr"
        }
      ],
      "source": {
        "advisory": "GHSA-6wx8-w4f5-wwcr",
        "discovery": "UNKNOWN"
      },
      "title": "concurrent-ruby: ReadWriteLock allows wrong-thread write release and stray read-release counter corruption"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-54906",
    "datePublished": "2026-06-24T15:46:01.116Z",
    "dateReserved": "2026-06-16T13:49:33.556Z",
    "dateUpdated": "2026-06-24T17:57:07.650Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-54906",
      "date": "2026-09-20",
      "epss": "0.00252",
      "percentile": "0.1699"
    },
    "microsoft_vex": {
      "current_release_date": "2026-06-30T15:41:31.000Z",
      "cve": "CVE-2026-54906",
      "id": "msrc_CVE-2026-54906",
      "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: ReadWriteLock allows wrong-thread write release and stray read-release counter corruption",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-54906.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::ReadWriteLock#release_write_lock does not verify that the calling thread acquired the write lock. Any thread with access to the lock object can release an active write lock held by another thread. A second writer can then enter its critical section while the first writer is still running. Concurrent::ReadWriteLock#release_read_lock also decrements the shared counter even when no read lock is held. Calling it on a fresh lock changes the counter from 0 to -1, after which normal read acquisition raises Concurrent::ResourceLimitError. This is a synchronization correctness issue in the public Concurrent::ReadWriteLock API. This vulnerability is fixed in 1.3.7."
          }
        ],
        "id": "CVE-2026-54906",
        "lastModified": "2026-06-26T20:00:16.700",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 9.8,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "HIGH",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
                "version": "3.1"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 5.9,
              "source": "nvd@nist.gov",
              "type": "Primary"
            }
          ],
          "cvssMetricV40": [
            {
              "cvssData": {
                "Automatable": "NOT_DEFINED",
                "Recovery": "NOT_DEFINED",
                "Safety": "NOT_DEFINED",
                "attackComplexity": "HIGH",
                "attackRequirements": "NONE",
                "attackVector": "LOCAL",
                "availabilityRequirement": "NOT_DEFINED",
                "baseScore": 2.1,
                "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": "NONE",
                "providerUrgency": "NOT_DEFINED",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "valueDensity": "NOT_DEFINED",
                "vectorString": "CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:N/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": "NONE",
                "vulnIntegrityImpact": "LOW",
                "vulnerabilityResponseEffort": "NOT_DEFINED"
              },
              "source": "security-advisories@github.com",
              "type": "Secondary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2026-54906",
                "options": [
                  {
                    "exploitation": "poc"
                  },
                  {
                    "automatable": "no"
                  },
                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-24T17:56:44.670673Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2026-06-24T17:17:29.550",
        "references": [
          {
            "source": "security-advisories@github.com",
            "tags": [
              "Third Party Advisory"
            ],
            "url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr"
          },
          {
            "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
            "tags": [
              "Third Party Advisory"
            ],
            "url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Analyzed",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-414"
              },
              {
                "lang": "en",
                "value": "CWE-667"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Low",
      "current_release_date": "2026-07-09T09:22:36+00:00",
      "cve": "CVE-2026-54906",
      "id": "CVE-2026-54906",
      "initial_release_date": "2026-06-24T15:46:01.116000+00:00",
      "product_status:known_not_affected": "20",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "concurrent-ruby: rubygem-concurrent-ruby: concurrent-ruby: Synchronization flaw in ReadWriteLock allows unauthorized lock release and denial of service",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-54906.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-08-31T16:39:09Z",
      "cve": "CVE-2026-54906",
      "id": "CVE-2026-54906",
      "initial_release_date": "2026-06-23T02:19:43Z",
      "product_status:known_affected": "86",
      "product_status:known_not_affected": "5",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2026-54906",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2026-54906.json",
      "version": "4"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2026-54906",
                    "options": [
                      {
                        "Exploitation": "poc"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2026-06-24T17:56:44.670673Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2026-06-24T17:57:02.851Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "references": [
              {
                "tags": [
                  "exploit"
                ],
                "url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr"
              }
            ],
            "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::ReadWriteLock#release_write_lock does not verify that the calling thread acquired the write lock. Any thread with access to the lock object can release an active write lock held by another thread. A second writer can then enter its critical section while the first writer is still running. Concurrent::ReadWriteLock#release_read_lock also decrements the shared counter even when no read lock is held. Calling it on a fresh lock changes the counter from 0 to -1, after which normal read acquisition raises Concurrent::ResourceLimitError. This is a synchronization correctness issue in the public Concurrent::ReadWriteLock API. This vulnerability is fixed in 1.3.7."
            }
          ],
          "metrics": [
            {
              "cvssV4_0": {
                "attackComplexity": "HIGH",
                "attackRequirements": "NONE",
                "attackVector": "LOCAL",
                "baseScore": 2.1,
                "baseSeverity": "LOW",
                "privilegesRequired": "NONE",
                "subAvailabilityImpact": "NONE",
                "subConfidentialityImpact": "NONE",
                "subIntegrityImpact": "NONE",
                "userInteraction": "NONE",
                "vectorString": "CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N",
                "version": "4.0",
                "vulnAvailabilityImpact": "LOW",
                "vulnConfidentialityImpact": "NONE",
                "vulnIntegrityImpact": "LOW"
              }
            }
          ],
          "problemTypes": [
            {
              "descriptions": [
                {
                  "cweId": "CWE-414",
                  "description": "CWE-414: Missing Lock Check",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            },
            {
              "descriptions": [
                {
                  "cweId": "CWE-667",
                  "description": "CWE-667: Improper Locking",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2026-06-24T15:46:01.116Z",
            "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
            "shortName": "GitHub_M"
          },
          "references": [
            {
              "name": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr",
              "tags": [
                "x_refsource_CONFIRM"
              ],
              "url": "https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr"
            }
          ],
          "source": {
            "advisory": "GHSA-6wx8-w4f5-wwcr",
            "discovery": "UNKNOWN"
          },
          "title": "concurrent-ruby: ReadWriteLock allows wrong-thread write release and stray read-release counter corruption"
        }
      },
      "cveMetadata": {
        "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "assignerShortName": "GitHub_M",
        "cveId": "CVE-2026-54906",
        "datePublished": "2026-06-24T15:46:01.116Z",
        "dateReserved": "2026-06-16T13:49:33.556Z",
        "dateUpdated": "2026-06-24T17:57:07.650Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.


Loading…

Loading…

Loading…

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…

Detection rules are retrieved from Rulezet.

Loading…

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…