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

> Concurrent requests can bypass single-use refresh token semantics, allowing multiple valid access tokens to be generated from a single leaked token.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Jun 2026
- **Updated:** 7 Aug 2026
- **Also known as:** GHSA-83r6-96m8-r52p

## What is CVE-2026-50631?

CVE-2026-50631 is a high-severity vulnerability in Apache Cxf, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2026-50631?

4 open source packages ship an affected version, including org.apache.cxf:cxf-rt-rs-security-oauth2. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `org.apache.cxf:cxf-rt-rs-security-oauth2` | Maven | All versions | 4.1.7 |
| `org.apache.cxf:cxf-rt-rs-security-oauth2` | Maven | All versions | 4.1.7 |
| `org.apache.cxf:cxf-rt-rs-security-oauth2` | Maven | From 4.2.0 | 4.2.2 |
| `org.apache.cxf:cxf-rt-rs-security-oauth2` | Maven | From 4.2.0 | 4.2.2 |

Products: Apache Cxf.

## How do I fix CVE-2026-50631?

Upgrade org.apache.cxf:cxf-rt-rs-security-oauth2 to a fixed version for your release line: 4.1.7 or 4.2.2.

## Is CVE-2026-50631 being exploited?

There is no known exploitation of CVE-2026-50631 in the wild and no public exploit code.

## Other vulnerabilities in Apache Cxf

- [CVE-2012-2379](https://insights.sbomify.com/CVE-2012-2379/): XML Signature/Encryption Not Validated in Apache CXF (critical 10.0)
- [CVE-2026-66909](https://insights.sbomify.com/CVE-2026-66909/): Apache CXF: Unsafe deserialization of inbound JMS ObjectMessage (critical 9.8)
- [CVE-2026-68079](https://insights.sbomify.com/CVE-2026-68079/): Apache CXF: DefaultEncryptingCodeDataProvider allows unlimited authorization code replay (critical 9.8)
- [CVE-2026-50628](https://insights.sbomify.com/CVE-2026-50628/): Apache CXF: OAuth2: Inverted IP Binding Check Defeats Security Control (critical 9.8)
- [CVE-2025-48913](https://insights.sbomify.com/CVE-2025-48913/): Apache CXF: Untrusted JMS configuration can lead to RCE (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-50631 and fix it if it is affected.

What it is: CVE-2026-50631 is a high-severity vulnerability in Apache Cxf, published on 12 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-50631 in the wild and no public exploit code.

Affected packages and fixed versions:
- org.apache.cxf:cxf-rt-rs-security-oauth2 (Maven): affected all versions; fixed in 4.1.7
- org.apache.cxf:cxf-rt-rs-security-oauth2 (Maven): affected all versions; fixed in 4.1.7
- org.apache.cxf:cxf-rt-rs-security-oauth2 (Maven): affected from 4.2.0; fixed in 4.2.2
- org.apache.cxf:cxf-rt-rs-security-oauth2 (Maven): affected from 4.2.0; fixed in 4.2.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-50631/ (Markdown: https://insights.sbomify.com/CVE-2026-50631/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-50631
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-50631
- OSV: https://osv.dev/vulnerability/CVE-2026-50631

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-50631/
Summaries are generated and may contain mistakes; the official description above is the record.