CVE-2026-50631: Apache CXF OAuth2 TOCTOU Race Condition in Refresh Token Processing

June 12, 2026 (updated August 20, 2026)

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.

References

github.com/advisories/GHSA-83r6-96m8-r52p
lists.apache.org/thread/s83t3x4r626o9h8rt0ryr1w7w53l1vv8
nvd.nist.gov/vuln/detail/CVE-2026-50631

Code Behaviors & Features

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