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NVD / CVE Program· CNA redhat

CVE-2021-20220: A flaw was found in Undertow.

MediumCVSS 4.8 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 19/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.2% (FIRST EPSS); higher than 68.5% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: undertow (Debian:14) 2.2.0-1; io.undertow:undertow-core (Maven) 2.1.6, 2.0.34; eap7-activemq-artemis (Red Hat:jboss_enterprise_application_platform:7.3::el6) 0:2.9.0-9.redhat_00019.1.el6eap.

Low priority for now. Upgrade to undertow (Debian:14) 2.2.0-1; io.undertow:undertow-core (Maven) 2.1.6, 2.0.34; eap7-activemq-artemis (Red Hat:jboss_enterprise_application_platform:7.3::el6) 0:2.9.0-9.redhat_00019.1.el6eap or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

A flaw was found in Undertow. A regression in the fix for CVE-2020-10687 was found. HTTP request smuggling related to CVE-2017-2666 is possible against HTTP/1.x and HTTP/2 due to permitting invalid characters in an HTTP request. This flaw allows an attacker to poison a web-cache, perform an XSS attack, or obtain sensitive information from request other than their own. The highest threat from this vulnerability is to data confidentiality and integrity.

Published
Feb 23, 2021
Updated
Jun 16, 2026
EPSS
1.2% · 68th percentile

Report tools

JSON

Action score

19

Monitor

Low priority for now.

CVSS
19 / 40 · 4.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.2%

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  • Not in KEV: no record of exploitation in the wild
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  • A fix has been released

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  • when exploit code appears or is weaponized
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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
redhatundertow
netappactive iq unified manager
netapponcommand workflow automation

Versions reported by the vendor

Affected version ranges reported by the assigning authority (redhat). Independent of NVD's CPE analysis and usually ahead of it.

  • n/a undertow

    • Undertow 2.2.0.Final, Undertow 2.1.6.Final, Undertow 2.0.34.Finalaffected
Affected versions · NVD (4)

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • netapp active iq unified managerall versions
  • netapp oncommand workflow automationall versions
  • redhat undertowbefore 2.0.34
  • redhat undertow2.1.0 and later · before 2.1.6

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:14undertowbefore 2.2.0-12.2.0-1
Mavenio.undertow:undertow-corefrom 2.1.0 · before 2.1.62.1.6
Mavenio.undertow:undertow-corebefore 2.0.342.0.34
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemisbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-clibefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-commonsbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-core-clientbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-dtobefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-hornetq-protocolbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-hqclient-protocolbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-jdbc-storebefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-jms-clientbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-jms-serverbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-journalbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-rabefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-selectorbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-serverbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-service-extensionsbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-activemq-artemis-toolsbefore 0:2.9.0-9.redhat_00019.1.el6eap0:2.9.0-9.redhat_00019.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-bouncycastlebefore 0:1.68.0-1.redhat_00001.1.el6eap0:1.68.0-1.redhat_00001.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-bouncycastle-mailbefore 0:1.68.0-1.redhat_00001.1.el6eap0:1.68.0-1.redhat_00001.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-bouncycastle-pkixbefore 0:1.68.0-1.redhat_00001.1.el6eap0:1.68.0-1.redhat_00001.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-bouncycastle-provbefore 0:1.68.0-1.redhat_00001.1.el6eap0:1.68.0-1.redhat_00001.1.el6eap
Red Hat:jboss_enterprise_application_platform:7.3::el6eap7-guavabefore 0:30.1.0-1.redhat_00001.1.el6eap0:30.1.0-1.redhat_00001.1.el6eap

+96

Same product

redhat: all records

Other highest-scoring records for the same primary product.

  • CVE-2020-1745A file inclusion vulnerability was found in the AJP connector enabled with a default AJP configuration port of 8009 in Undertow version 2.0.
    40Plan
  • CVE-2019-10212A flaw was found in, all under 2.0.20, in the Undertow DEBUG log for io.undertow.request.security.
    40Plan
  • CVE-2019-3888A vulnerability was found in Undertow web server before 2.0.21.
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2020-10705Jun 10, 2020 · A flaw was discovered in Undertow in versions before Undertow 2.1.1.Final where certain requests to the "Expect: 100-continue" header may…
    30Monitor
  • ← EarlierCVE-2020-10687Sep 23, 2020 · A flaw was discovered in all versions of Undertow before Undertow 2.2.0.Final, where HTTP request smuggling related to CVE-2017-2666 is…
    19Monitor
  • Later →CVE-2023-3223Sep 27, 2023 · Undertow: outofmemoryerror due to @multipartconfig handling
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
debian:undertow2.2.0-1 · Debian:14Package registry (OSV)
Maven:io.undertow:undertow-core2.0.34Package registry (OSV)
Maven:io.undertow:undertow-core2.1.6Package registry (OSV)
red hat:eap7-activemq-artemis0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-cli0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-commons0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-core-client0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-dto0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-hornetq-protocol0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-hqclient-protocol0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-jdbc-store0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-jms-client0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-jms-server0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-journal0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)
red hat:eap7-activemq-artemis-ra0:2.9.0-9.redhat_00019.1.el6eap · Red Hat:jboss_enterprise_application_platform:7.3::el6Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
low · data can be read
Integrity
low · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
Low
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records