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Fencer Vulns
high 7.5

CVE-2020-27782 json

Denial of service in Undertow

published 2021-02-23 5 y ago modified 2026-06-17 4 mo ago also GHSA-rhcw-wjcm-9h6g , EUVD-2022-1173

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.4%
EPSS 1.4% chance of exploitation in 30 days, percentile 72%
public exploits
0
none known

Summary

A flaw was found in the Undertow AJP connector. Malicious requests and abrupt connection closes could be triggered by an attacker using query strings with non-RFC compliant characters resulting in a denial of service. The highest threat from this vulnerability is to system availability. This affects Undertow 2.1.5.SP1, 2.0.33.SP2, and 2.2.3.SP1.

Patch / fix

  • maven io.undertow:undertow-core 2.0.33, 2.1.5
  • undertow Debian 14 2.2.4-1

debian advisories DEBIAN-CVE-2020-27782

  • eap7-wildfly jboss enterprise application platform 7.3 7.3.5-2.GA_redhat_00001.1.el8eap
  • eap7-narayana jboss enterprise application platform 7.3 5.9.10-1.Final_redhat_00001.1.el8eap
  • eap7-resteasy jboss enterprise application platform 7.3 3.11.3-1.Final_redhat_00001.1.el8eap
  • eap7-undertow jboss enterprise application platform 7.3 2.0.33-1.SP2_redhat_00001.1.el8eap
  • eap7-hibernate jboss enterprise application platform 7.3 5.3.20-1.Final_redhat_00001.1.el8eap
  • eap7-hal-console jboss enterprise application platform 7.3 3.2.12-1.Final_redhat_00001.1.el8eap
  • eap7-resteasy-cdi jboss enterprise application platform 7.3 3.11.3-1.Final_redhat_00001.1.el8eap
  • eap7-glassfish-jsf jboss enterprise application platform 7.3 2.3.9-12.SP13_redhat_00001.1.el8eap

red hat advisories RHSA-2025:9582RHSA-2021:0248RHSA-2021:0247RHSA-2021:0246

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-27782 updated cvss 7.5

undertow: special character in query results in server errors

  • Red Hat Integration Camel K 1 undertow undertow Red Hat Integration Camel Quarkus 1 undertow undertow
    affected: workaround, no fix available “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.”
  • Red Hat JBoss Data Grid 7 undertow undertow
    affected: workaround, no fix planned “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.”
  • Red Hat JBoss Fuse 6 undertow undertow Red Hat OpenShift Application Runtimes undertow undertow
    affected: workaround, no fix available “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.”
  • Red Hat OpenStack Platform 13 (Queens) opendaylight
    affected: workaround, no fix planned “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.”
  • Red Hat support for Spring Boot undertow undertow
    affected: workaround, no fix available “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.”
  • Red Hat Fuse 7.10
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:5134
  • Red Hat Integration
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:3205
  • Red Hat Integration Camel Quarkus 2
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:3207
show 9 more
  • Red Hat JBoss EAP 7.3 for BaseOS-8 eap7-wildfly 7.3.5-2.GA_redhat_00001.1.el8eap, eap7-undertow 2.0.33-1.SP2_redhat_00001.1.el8eap, eap7-narayana 5.9.10-1.Final_redhat_00001.1.el8eap, eap7-resteasy 3.11.3-1.Final_redhat_00001.1.el8eap, eap7-activemq-artemis 2.9.0-7.redhat_00017.1.el8eap, eap7-hibernate 5.3.20-1.Final_redhat_00001.1.el8eap, +90 more
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:0248
  • Red Hat JBoss EAP 7.3 for RHEL 6 Server eap7-wildfly 7.3.5-2.GA_redhat_00001.1.el6eap, eap7-undertow 2.0.33-1.SP2_redhat_00001.1.el6eap, eap7-narayana 5.9.10-1.Final_redhat_00001.1.el6eap, eap7-resteasy 3.11.3-1.Final_redhat_00001.1.el6eap, eap7-activemq-artemis 2.9.0-7.redhat_00017.1.el6eap, eap7-hibernate 5.3.20-1.Final_redhat_00001.1.el6eap, +90 more
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:0246
  • Red Hat JBoss EAP 7.3 for RHEL 7 Server eap7-wildfly 7.3.5-2.GA_redhat_00001.1.el7eap, eap7-undertow 2.0.33-1.SP2_redhat_00001.1.el7eap, eap7-narayana 5.9.10-1.Final_redhat_00001.1.el7eap, eap7-resteasy 3.11.3-1.Final_redhat_00001.1.el7eap, eap7-activemq-artemis 2.9.0-7.redhat_00017.1.el7eap, eap7-hibernate 5.3.20-1.Final_redhat_00001.1.el7eap, +92 more
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:0247
  • Red Hat JBoss Enterprise Application Platform 7
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:0250
  • Red Hat JBoss Enterprise Application Platform 7.1 EUS for RHEL 7 Server eap7-wildfly 7.1.11-4.GA_redhat_00002.1.ep7.el7, eap7-netty 4.1.63-2.Final_redhat_00003.1.ep7.el7, eap7-undertow 1.4.18-16.SP14_redhat_00001.1.ep7.el7, eap7-glassfish-el 3.0.1-4.b08_redhat_00005.1.ep7.el7, eap7-hibernate 5.1.17-3.Final_redhat_00004.1.ep7.el7, eap7-netty-all 4.1.63-2.Final_redhat_00003.1.ep7.el7, +19 more
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2025:9582
  • Red Hat Single Sign-On 7.4.5
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:0327
  • Red Hat support for Spring Boot 2.3.10
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:3425
  • Red Hat Text-Only RHOAR
    fixed: vendor fix “The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.” RHSA-2021:0295
  • Red Hat build of Quarkus undertow undertow Red Hat Decision Manager 7 undertow undertow Red Hat Integration Service Registry undertow undertow Red Hat Process Automation 7 undertow undertow
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

1.38% chance of exploitation in the next 30 days, higher than 72% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 7.8 AV:N/AC:L/Au:N/C:N/I:N/A:C
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
maven io.undertow:undertow-core
>=2.1.0, <2.1.5
<2.0.33
2.1.5
2.0.33

Affected products

  • n/a Undertow

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.