CVE-2021-3859

Undertow vulnerable to Denial of Service (DoS) attacks

7.5 HighFix available

A flaw was found in Undertow that tripped the client-side invocation timeout with certain calls made over HTTP2. This flaw allows an attacker to carry out denial of service attacks.

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: None
Integrity: None
Availability: High

Exploit likelihood

1.74%Up 0.8 points since Aug 27, 2022

What each source reports

NVD Score used 7.5

A flaw was found in Undertow that tripped the client-side invocation timeout with certain calls made over HTTP2. This flaw allows an attacker to carry out denial of service attacks.

Record: CVE-2021-3859
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-214, CWE-668
Updated: 2026-11-02

CVE List No score

A flaw was found in Undertow that tripped the client-side invocation timeout with certain calls made over HTTP2. This flaw allows an attacker to carry out denial of service attacks.

Record: CVE-2021-3859
Weakness: CWE-214
Updated: 2026-11-02

EUVDEUVD-2022-6212 No score

A flaw was found in Undertow that tripped the client-side invocation timeout with certain calls made over HTTP2. This flaw allows an attacker to carry out denial of service attacks.

Record: EUVD-2022-6212
Updated: 2026-11-03

GitHub AdvisoriesGHSA-339q-62wm-c39w 7.5

Undertow vulnerable to Denial of Service (DoS) attacks

Undertow client side invocation timeout raised when calling over HTTP2, this vulnerability can allow attacker to carry out denial of service (DoS) attacks in versions less than 2.2.15 Final.

Record: GHSA-339q-62wm-c39w
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-214, CWE-400, CWE-668
Updated: 2026-11-02

OSV 7.5

A flaw was found in Undertow that tripped the client-side invocation timeout with certain calls made over HTTP2. This flaw allows an attacker to carry out denial of service attacks.

Record: CVE-2021-3859
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVDEBIAN-CVE-2021-3859 7.5

A flaw was found in Undertow that tripped the client-side invocation timeout with certain calls made over HTTP2. This flaw allows an attacker to carry out denial of service attacks.

Record: DEBIAN-CVE-2021-3859
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Show 9 moreShow less

OSVGHSA-339q-62wm-c39w 7.5

Undertow vulnerable to Denial of Service (DoS) attacks

Undertow client side invocation timeout raised when calling over HTTP2, this vulnerability can allow attacker to carry out denial of service (DoS) attacks in versions less than 2.2.15 Final.

Record: GHSA-339q-62wm-c39w
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness: CWE-214, CWE-400, CWE-668
Updated: 2026-11-02

OSVRHSA-2022:0400 7.5

Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 7.4.3 security update

Record: RHSA-2022:0400
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVRHSA-2022:0401 7.5

Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 7.4.3 security update

Record: RHSA-2022:0401
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVRHSA-2022:0405 7.5

Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 7.3 security update

Record: RHSA-2022:0405
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVRHSA-2022:0447 8.8

Red Hat Security Advisory: Red Hat Single Sign-On 7.5.1 security update on RHEL 7

Record: RHSA-2022:0447
CVSS 3.1: 8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVRHSA-2022:0448 8.8

Red Hat Security Advisory: Red Hat Single Sign-On 7.5.1 security update on RHEL 8

Record: RHSA-2022:0448
CVSS 3.1: 8.8 HighCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVRHSA-2024:10207 9.8

Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 7.3.11 Security update

Record: RHSA-2024:10207
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVRHSA-2025:4226 7.5

Red Hat Security Advisory: Red Hat JBoss Enterprise Application Platform 7.1.10 on RHEL 7 security update

Record: RHSA-2025:4226
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-3859 7.5

A flaw was found in Undertow that tripped the client-side invocation timeout with certain calls made over HTTP2. This flaw allows an attacker to carry out denial of service attacks.

Record: UBUNTU-CVE-2021-3859
CVSS 3.1: 7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`io.undertow:undertow-core` Maven	before 2.2.15	2.2.15
`undertow` Debian:14	before 2.2.16-1, plus listed versions 1.3.11-11.3.16-11.3.19-11.3.21-11.3.23-1 Show 40 moreShow less 1.3.4-11.3.5-11.3.7-11.4.0-11.4.1-11.4.18-11.4.20-11.4.21-11.4.21-21.4.22-11.4.23-11.4.23-21.4.23-31.4.25-11.4.25-21.4.3-11.4.4-11.4.6-11.4.7-11.4.8-12.0.23-12.0.25-12.0.26-12.0.27-12.0.28-12.0.29-12.0.30-12.1.0-12.1.1-12.1.3-12.2.0-12.2.10-12.2.12-12.2.13-12.2.14-12.2.2-12.2.3-12.2.4-12.2.5-12.2.8-1	2.2.16-1
`io.undertow:undertow-core` Maven	before 2.2.15, plus listed versions 1.0.0.Alpha11.0.0.Alpha101.0.0.Alpha111.0.0.Alpha121.0.0.Alpha13 Show 45 moreShow less 1.0.0.Alpha141.0.0.Alpha151.0.0.Alpha161.0.0.Alpha171.0.0.Alpha181.0.0.Alpha191.0.0.Alpha21.0.0.Alpha201.0.0.Alpha211.0.0.Alpha221.0.0.Alpha31.0.0.Alpha41.0.0.Alpha51.0.0.Alpha61.0.0.Alpha71.0.0.Alpha81.0.0.Alpha91.0.0.Beta11.0.0.Beta101.0.0.Beta111.0.0.Beta121.0.0.Beta131.0.0.Beta141.0.0.Beta151.0.0.Beta161.0.0.Beta171.0.0.Beta181.0.0.Beta191.0.0.Beta21.0.0.Beta201.0.0.Beta211.0.0.Beta221.0.0.Beta231.0.0.Beta241.0.0.Beta251.0.0.Beta261.0.0.Beta271.0.0.Beta281.0.0.Beta291.0.0.Beta31.0.0.Beta301.0.0.Beta311.0.0.Beta321.0.0.Beta331.0.0.Beta4	2.2.15
`eap7-undertow` Red Hat:jboss_enterprise_application_platform:7.4::el7	before 0:2.2.13-1.SP2_redhat_00001.1.el7eap	0:2.2.13-1.SP2_redhat_00001.1.el7eap
`eap7-hornetq` Red Hat:jboss_enterprise_application_platform:7.4::el7	before 0:2.4.8-1.Final_redhat_00001.1.el7eap	0:2.4.8-1.Final_redhat_00001.1.el7eap
`eap7-hornetq-commons` Red Hat:jboss_enterprise_application_platform:7.4::el7	before 0:2.4.8-1.Final_redhat_00001.1.el7eap	0:2.4.8-1.Final_redhat_00001.1.el7eap
`eap7-hornetq-core-client` Red Hat:jboss_enterprise_application_platform:7.4::el7	before 0:2.4.8-1.Final_redhat_00001.1.el7eap	0:2.4.8-1.Final_redhat_00001.1.el7eap
`eap7-hornetq-jms-client` Red Hat:jboss_enterprise_application_platform:7.4::el7	before 0:2.4.8-1.Final_redhat_00001.1.el7eap	0:2.4.8-1.Final_redhat_00001.1.el7eap
`eap7-undertow` Red Hat:jboss_enterprise_application_platform:7.4::el8	before 0:2.2.13-1.SP2_redhat_00001.1.el8eap	0:2.2.13-1.SP2_redhat_00001.1.el8eap
`eap7-hornetq` Red Hat:jboss_enterprise_application_platform:7.4::el8	before 0:2.4.8-1.Final_redhat_00001.1.el8eap	0:2.4.8-1.Final_redhat_00001.1.el8eap

Show 91 moreShow less

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases, products	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-3859 is a high vulnerability (CVSS 7.5) in Red Hat Undertow, published July 15, 2022. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.74%, the 77th percentile. Fixed in io.undertow:undertow-core 2.2.15.

References

Show 194 moreShow less

This page doesn't list everything

Left out here: 233 versions and 13 references. The JSON record has them.

Affected packages
Package	Affected	Fixed
`eap7-hornetq-commons` Red Hat:jboss_enterprise_application_platform:7.4::el8	before 0:2.4.8-1.Final_redhat_00001.1.el8eap	0:2.4.8-1.Final_redhat_00001.1.el8eap
`eap7-hornetq-core-client` Red Hat:jboss_enterprise_application_platform:7.4::el8	before 0:2.4.8-1.Final_redhat_00001.1.el8eap	0:2.4.8-1.Final_redhat_00001.1.el8eap
`eap7-hornetq-jms-client` Red Hat:jboss_enterprise_application_platform:7.4::el8	before 0:2.4.8-1.Final_redhat_00001.1.el8eap	0:2.4.8-1.Final_redhat_00001.1.el8eap
`eap7-undertow` Red Hat:jboss_enterprise_application_platform:7.3::el6	before 0:2.0.41-2.SP2_redhat_00001.1.el6eap	0:2.0.41-2.SP2_redhat_00001.1.el6eap
`eap7-undertow` Red Hat:jboss_enterprise_application_platform:7.3::el7	before 0:2.0.41-2.SP2_redhat_00001.1.el7eap	0:2.0.41-2.SP2_redhat_00001.1.el7eap
`eap7-undertow` Red Hat:jboss_enterprise_application_platform:7.3::el8	before 0:2.0.41-2.SP2_redhat_00001.1.el8eap	0:2.0.41-2.SP2_redhat_00001.1.el8eap
`rh-sso7-keycloak` Red Hat:red_hat_single_sign_on:7.5::el7	before 0:15.0.4-1.redhat_00003.1.el7sso	0:15.0.4-1.redhat_00003.1.el7sso
`rh-sso7-keycloak-server` Red Hat:red_hat_single_sign_on:7.5::el7	before 0:15.0.4-1.redhat_00003.1.el7sso	0:15.0.4-1.redhat_00003.1.el7sso
`rh-sso7-keycloak` Red Hat:red_hat_single_sign_on:7.5::el8	before 0:15.0.4-1.redhat_00003.1.el8sso	0:15.0.4-1.redhat_00003.1.el8sso
`rh-sso7-keycloak-server` Red Hat:red_hat_single_sign_on:7.5::el8	before 0:15.0.4-1.redhat_00003.1.el8sso	0:15.0.4-1.redhat_00003.1.el8sso
`eap7-apache-cxf` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:3.4.10-1.SP1_redhat_00001.1.el7eap	0:3.4.10-1.SP1_redhat_00001.1.el7eap
`eap7-apache-cxf-rt` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:3.4.10-1.SP1_redhat_00001.1.el7eap	0:3.4.10-1.SP1_redhat_00001.1.el7eap
`eap7-apache-cxf-services` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:3.4.10-1.SP1_redhat_00001.1.el7eap	0:3.4.10-1.SP1_redhat_00001.1.el7eap
`eap7-apache-cxf-tools` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:3.4.10-1.SP1_redhat_00001.1.el7eap	0:3.4.10-1.SP1_redhat_00001.1.el7eap
`eap7-avro` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.6-8.redhat_00003.1.el7eap	0:1.7.6-8.redhat_00003.1.el7eap
`eap7-h2database` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.4.197-3.redhat_00004.1.el7eap	0:1.4.197-3.redhat_00004.1.el7eap
`eap7-jboss-annotations-api_1.3_spec` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:2.0.1-4.Final_redhat_00001.1.el7eap	0:2.0.1-4.Final_redhat_00001.1.el7eap
`eap7-jboss-marshalling` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:2.0.15-1.Final_redhat_00001.1.el7eap	0:2.0.15-1.Final_redhat_00001.1.el7eap
`eap7-jboss-marshalling-river` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:2.0.15-1.Final_redhat_00001.1.el7eap	0:2.0.15-1.Final_redhat_00001.1.el7eap
`eap7-jboss-server-migration` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-cli` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-core` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-eap6.4` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-eap6.4-to-eap7.3` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-eap7.0` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-eap7.1` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-eap7.2` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-eap7.2-to-eap7.3` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-eap7.3-server` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly10.0` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly10.1` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly11.0` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly12.0` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly13.0-server` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly14.0-server` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly15.0-server` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly16.0-server` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly17.0-server` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly18.0-server` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap
`eap7-jboss-server-migration-wildfly8.2` Red Hat:jboss_enterprise_application_platform_eus:7.3::el7	before 0:1.7.2-12.Final_redhat_00013.1.el7eap	0:1.7.2-12.Final_redhat_00013.1.el7eap