# Apache CXF OAuth2 TOCTOU Race Condition in Refresh Token Processing

Advisory record · `GHSA-83r6-96m8-r52p`

- **Identifiers:** `GHSA-83r6-96m8-r52p` · `CVE-2026-50631`
- **State:** Confirmed
- **Severity:** CVSS 7.4 High
- **Critical:** No
- **Weakness (CWE):** [CWE-367](https://cwe.mitre.org/data/definitions/367.html)
- **Tags:** [Race condition](https://agentprime.io/advisories/tag/race-condition.md)
- **Published:** 12 Jun 2026
- **Updated:** 20 Aug 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 12 Jun 2026, 12:31 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `org.apache.cxf:cxf-rt-rs-security-oauth2` (Maven): affected `>=4.2.0, <4.2.2 || <4.1.7`; fixed in `4.2.2`, `4.1.7`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Apache CXF's cxf-rt-rs-security-oauth2 package, versions 4.2.0 up to but not including 4.2.2 and versions below 4.1.7, has a race condition in refresh token processing. When recycleRefreshTokens is set to false, concurrent requests using the same refresh token can each obtain a valid access token, bypassing single-use behavior. An attacker who has obtained a leaked refresh token can exploit this by replaying it concurrently. Upgrade to version 4.2.2 or 4.1.7.

Written 2 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.4 High, CVSS 3.1: `CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`, from GitHub Advisory Database

- **CISA KEV:** Not listed.
- **EPSS:** 0.0027, the 19th percentile, on 9 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 12 Jun 2026, 10:16 UTC: [Confirmed by NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-50631)
- 31 Oct 2026, 14:19 UTC: First seen by agentprime
- 31 Oct 2026, 14:19 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-83r6-96m8-r52p)

## Sources

- [GitHub Advisory Database: GHSA-83r6-96m8-r52p](https://github.com/advisories/GHSA-83r6-96m8-r52p)
- [OSV: GHSA-83r6-96m8-r52p](https://osv.dev/vulnerability/GHSA-83r6-96m8-r52p)
- <https://nvd.nist.gov/vuln/detail/CVE-2026-50631>
- <https://github.com/apache/cxf>
- <https://lists.apache.org/thread/s83t3x4r626o9h8rt0ryr1w7w53l1vv8>
- <http://www.openwall.com/lists/oss-security/2026/06/11/8>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-83r6-96m8-r52p>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-83r6-96m8-r52p/>. Everything for agents: <https://agentprime.io/llms.txt>.