Race Condition in OAuth Refresh Token Single-Use Bypass

A race condition in AbstractOAuthDataProvider allows concurrent requests using the same Refresh Token to bypass single-use semantics and generate multiple valid Access Tokens, when 'recycleRefreshTokens' is set to false. A leaked refresh token can be replayed concurrently by multiple attackers or threads. Users are recommended to upgrade to versions 4.2.2 or 4.1.7, which fixes this issue.

Casky was already ahead

This CVE exploits attack patterns that Casky's 203matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

CVE-2026-50631 exposes a critical race condition in AbstractOAuthDataProvider where concurrent requests using the same refresh token can circumvent single-use semantics when 'recycleRefreshTokens' is disabled. This allows attackers to generate multiple valid access tokens from a single leaked refresh token, effectively multiplying the window of compromise. Any organization using affected versions with this configuration enabled is vulnerable—particularly those handling sensitive OAuth flows in high-concurrency environments. A compromised refresh token becomes exponentially more dangerous, as attackers can spawn parallel requests to instantly obtain numerous valid session tokens before detection mechanisms trigger.

Casky's 203 aligned skills leverage Claude's extended reasoning to identify the attack patterns underlying this vulnerability across MITRE ATT&CK technique TA0004 (Privilege Escalation). Practitioners using Casky would detect suspicious indicators including: concurrent token refresh requests originating from different IP addresses or user agents within millisecond windows; unusual spikes in access token issuance without corresponding user authentication events; and refresh token reuse patterns that violate expected single-use behavior. The platform's skills map these behavioral anomalies to token replay and session hijacking attack chains, enabling security teams to correlate logs across identity providers, API gateways, and application servers to confirm exploitation before attackers establish persistent access.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →

203 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-50631.

analyzing-cloud-storage-access-patterns

cloud security · low

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analyzing-kubernetes-audit-logs

container security · low

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analyzing-office365-audit-logs-for-compromise

cloud security · low

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MITRE ATT&CK Techniques

TA0004

Investigate the attack patterns behind CVE-2026-50631

Casky has 203 skills that investigate the attack patterns behind CVE-2026-50631. Run one and get CVSS-scored findings in 3 minutes.

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