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Apache CXF OAuth2 TOCTOU Race Condition in Refresh Token Processing

High severity GitHub Reviewed Published Jun 12, 2026 to the GitHub Advisory Database • Updated Aug 20, 2026

Package

maven org.apache.cxf:cxf-rt-rs-security-oauth2 (Maven)

Affected versions

>= 4.2.0, < 4.2.2
< 4.1.7

Patched versions

4.2.2
4.1.7

Description

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

Published by the National Vulnerability Database Jun 12, 2026
Published to the GitHub Advisory Database Jun 12, 2026
Reviewed Aug 20, 2026
Last updated Aug 20, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(20th percentile)

Weaknesses

Time-of-check Time-of-use (TOCTOU) Race Condition

The product 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. Learn more on MITRE.

CVE ID

CVE-2026-50631

GHSA ID

GHSA-83r6-96m8-r52p

Source code

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