Apache OAuth (AbstractOAuthDataProvider) Race Condition, fixed in 4.2.2/4.1.7
CVE-2026-50631 Published on June 12, 2026
Apache CXF: OAuth2: TOCTOU Race Condition in Refresh Token Processing
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.
Vulnerability Analysis
CVE-2026-50631 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality and integrity, and no impact on availability.
Weakness Type
What is a TOCTTOU Vulnerability?
The software checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the software to perform invalid actions when the resource is in an unexpected state. This weakness can be security-relevant when an attacker can influence the state of the resource between check and use. This can happen with shared resources such as files, memory, or even variables in multithreaded programs.
CVE-2026-50631 has been classified to as a TOCTTOU vulnerability or weakness.
Products Associated with CVE-2026-50631
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Affected Versions
Apache Software Foundation Apache CXF:- Version 4.2.0 and below 4.2.2 is affected.
- Before 4.1.7 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.