OAuth 2 authorization service vulnerable to DDos attacks (CVE-2021-22696)
Published Sources: Red Hat, CVE.org, OSV
What is affected, what to do
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.
Update Apache CXF to version 3.4.3, Apache CXF to version 3.3.10.
- Affected
- Apache CXF
lt *..3.4.3 - Apache CXF
lt *..3.3.10
- Apache CXF
- Fixed in
- Apache CXF
3.4.3 - Apache CXF
3.3.10
- Apache CXF
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Metrics
7.5
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: NVD, CVSS v3
7.5
CVSS v3
Severity High on the scale from 0 to 10.
Source: Red Hat, CVE.org, OSV
6.6 %
EPSS score
Moderate — model estimates 1-10% exploitation likelihood.
Source: FIRST EPSS, percentile 93.8
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 107.95 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- no public PoC known
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 7.5 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 7.5
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 6.6 %
- Moderate — model estimates 1-10% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 93.8
- Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-918, CWE-400
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
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.
Source: redhat_csaf, NVD (NIST), OSV (Open Source Vulnerabilities), cvelistv5
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Apache Software Foundation | Apache CXF |
|
|
| apache | cxf |
|
|
| oracle | business_intelligence |
|
|
| oracle | communications_diameter_intelligence_hub |
|
|
| oracle | communications_element_manager |
|
|
| oracle | communications_session_report_manager |
|
|
| oracle | communications_session_route_manager |
|
|
| maven | org.apache.cxf:apache-cxf |
|
|
Vendors and products
Weakness classes (CWE)
CWE-918Server-Side Request Forgery (SSRF)
Base
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
Entry at MITRE CWE-918CWE-400Uncontrolled Resource Consumption
Class
The product does not properly control the allocation and maintenance of a limited resource.
Entry at MITRE CWE-400
References & sources
- NVD (NIST)vuln/detail/CVE-2021-22696advisory
- github.comapache/cxf/commit/40503a53914758759894f704bbf139ae89ace286web
- github.comapache/cxf/commit/aa789c5c4686597a7bdef2443909ab491fc2bc04web
- cxf.apache.orgsecurity-advisories.data/CVE-2021-22696.txt.ascweb, x_refsource_MISC, Vendor advisory
- github.comapache/cxfpackage
- lists.apache.orgthread.html/r6445001cc5f9a2bb1e6316993753306e054bdd1d702656b7cb…web
- lists.apache.orgthread.html/r8651c06212c56294a1c0ea61a5ad7790c06502209c03f05c0c…web
- lists.apache.orgthread.html/r8651c06212c56294a1c0ea61a5ad7790c06502209c03f05c0c…web
- lists.apache.orgthread.html/rec7160382badd3ef4ad017a22f64a266c7188b9ba71394f0d3…web
- lists.apache.orgthread.html/rfb87e0bf3995e7d560afeed750fac9329ff5f1ad49da365129…web
- oracle.comsecurity-alerts/cpuapr2022.htmlweb, x_refsource_MISC, Patch, Third-party advisory
- oracle.comsecurity-alerts/cpuoct2021.htmlweb, x_refsource_MISC, Patch, Third-party advisory
- openwall.com[oss-security] 20210402 CVE-2021-22696: Apache CXF: OAuth 2 authorization service vulnerable to DDos attacksweb, Mailing list, x_refsource_MLIST, Mailing list, Third-party advisory
- lists.apache.org[cxf-dev] 20210402 CVE-2021-22696: OAuth 2 authorization service vulnerable to DDos attacksMailing list, x_refsource_MLIST
- lists.apache.org[cxf-users] 20210402 CVE-2021-22696: OAuth 2 authorization service vulnerable to DDos attacksMailing list, x_refsource_MLIST
- lists.apache.org[cxf-commits] 20210402 svn commit: r1073270 - in /websites/production/cxf/content: cache/main.pageCache security-advisories.data/CVE-2021-22696.txt.asc security-advisories.htmlMailing list, x_refsource_MLIST
- lists.apache.org[announce] 20210402 [Apache CXF] CVE-2021-22696: OAuth 2 authorization service vulnerable to DDos attacksMailing list, x_refsource_MLIST
- lists.apache.org[cxf-commits] 20210616 svn commit: r1075801 - in /websites/production/cxf/content: cache/main.pageCache index.html security-advisories.data/CVE-2021-30468.txt.asc security-advisories.htmlMailing list, x_refsource_MLIST
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<a href="https://intel.neosec.eu/en/cve/CVE-2021-22696"><img src="https://intel.neosec.eu/badge/cve/CVE-2021-22696.svg?lang=en" alt="CVE-2021-22696 – NEOSEC Intel" height="20"></a>