How severe is CVE-2021-28164?

CVE-2021-28164 has a CVSS score of 5.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-28164?

CVE-2021-28164 affects the following packages: org.eclipse.jetty:jetty-webapp (Maven). Ecosystems affected: Maven.

How do I fix CVE-2021-28164?

Update org.eclipse.jetty:jetty-webapp to 9.4.39 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-28164 is resolved across your whole dependency graph.

How do I detect CVE-2021-28164 in my Maven dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.eclipse.jetty:jetty-webapp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-28164 if there is no patch (or I can't update yet)?

Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Is CVE-2021-28164 actively exploited in the wild?

Yes. There are 3 known exploit references for CVE-2021-28164, including 1 documented proof-of-concept exploit on Exploit-DB and 2 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-28164?

CVE-2021-28164 has an EPSS (Exploit Prediction Scoring System) score of 82.4%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

What type of vulnerability is CVE-2021-28164?

CVE-2021-28164 is classified as Information Exposure (CWE-200), CWE-551 (CWE-551). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Is there exploit tooling available for CVE-2021-28164?

A Nuclei detection template exists for CVE-2021-28164, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2021-28164 published, and has it been updated?

CVE-2021-28164 was published on April 1, 2021 and was last updated on October 24, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕

☕ Maven

Not in CISA KEV

MEDIUM severity

CVE-2021-28164 — jetty-webapp

MEDIUM

CVE-2021-28164 is a medium-severity (CVSS 5.3) Information Exposure vulnerability in org.eclipse.jetty:jetty-webapp. 3 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for org.eclipse.jetty:jetty-webapp — see the affected versions and patch details below.

Authorization Before Parsing and Canonicalization in jetty

Also known asGHSA-v7ff-8wcx-gmc5

Published

Apr 1, 2021

Updated

Oct 24, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

3 known

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

82.4%probability of exploitation in next 30 days

Very High Risk0.00%

Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

☕org.eclipse.jetty:jetty-webapp

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

Release 9.4.37 introduced a more precise implementation of RFC3986 with regards to URI decoding, together with some new compliance modes to optionally allow support of some URI that may have ambiguous interpretation within the Servlet specified API methods behaviours. The default mode allowed % encoded . characters to be excluded for URI normalisation, which is correct by the RFC, but is not assumed by common Servlet implementations. The default compliance mode allows requests with URIs that contain %2e or %2e%2e segments to access protected resources within the WEB-INF directory. For example a request to /context/%2e/WEB-INF/web.xml can retrieve the web.xml file. This can reveal sensitive information regarding the implementation of a web application. Workarounds found by HttpCompliance mode RFC7230_NO_AMBIGUOUS_URIS can be enabled by updating start.d/http.ini to include: jetty.http.compliance=RFC7230_NO_AMBIGUOUS_URIS.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.eclipse.jetty:jetty-webapp`	≥ 9.4.37&&< 9.4.39	9.4.39`org.eclipse.jetty:jetty-webapp:9.4.39`

Affected Products

17 products · 20 configurations

Application

jettyeclipse

2 versions

9.4.379.4.38

Application

cloud managernetapp

all

Application

e-series performance analyzernetapp

all

Application

e-series santricity os controllernetapp

≥ 11.0 && ≤ 11.70.1

range

Application

e-series santricity web servicesnetapp

all

Application

element plug-in for vcenter servernetapp

all

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-50438webappsjava

Jetty 9.4.37.v20210219 - Information Disclosure

by Mayank Deshmukh · Oct 22, 2021

Exploit-DB Source

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.eclipse.jetty:jetty-webapp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.eclipse.jetty:jetty-webapp to 9.4.39 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-28164 is resolved across your whole dependency graph.
Workarounds
Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

How to detect CVE-2021-28164

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2021-28164 -u https://target

Template: Eclipse Jetty - Information Disclosure
Severity: medium
Impact: An attacker can exploit this vulnerability to access sensitive information, potentially leading to further attacks or unauthorized access.
Remediation: Apply the latest security patches or updates provided by the Eclipse Jetty project to fix the information disclosure vulnerability.

Template by ProjectDiscovery nuclei-templates (noamrathaus), MIT licensed. View the full template. Scan only systems you are authorised to test.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Red Hat OpenStack Platform's OpenDaylight will not be updated for this flaw because it was deprecated as of OpenStack Platform 14 and is only receiving security fixes for Important and Critical flaws. Red Hat CodeReady Studio 12 is not affected by this vulnerability because it does not ship a vulnerable version of…

Product	Fixed in	Advisory
Red Hat AMQ 7.8.2	`jetty-server`	RHSA-2021:2689
Red Hat AMQ 7.9.0	see advisory	RHSA-2021:3700
Red Hat AMQ Streams 1.6.4	see advisory	RHSA-2021:1560
Red Hat AMQ Streams 1.8.0	`jetty-server`	RHSA-2021:3225
Red Hat Developer Tools	`rh-eclipse-jetty-0:9.4.40-1.1.el7_9`	RHSA-2021:1509
Red Hat Fuse 7.10	`jetty`	RHSA-2021:5134
Red Hat Integration Camel Quarkus 2	see advisory	RHSA-2021:4767
RHAF Camel-K 1.8	`jetty`	RHSA-2022:6407

Frequently Asked Questions

Release 9.4.37 introduced a more precise implementation of [RFC3986](https://tools.ietf.org/html/rfc3986#section-3.3) with regards to URI decoding, together with some new compliance modes to optionally allow support of some URI that may have ambiguous interpretation within the Servlet specified API methods behaviours. The default mode allowed % encoded . characters to be excluded for URI normalisation, which is correct by the RFC, but is not assumed by common Servlet implementations. The default compliance mode allows requests with URIs that contain `%2e` or `%2e%2e` segments to access prote

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