CVE-2020-27782 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in io.undertow:undertow-core. A fix is available for io.undertow:undertow-core — see the affected versions and patch details below.
Denial of service in Undertow
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2020-27782 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
io.undertow:undertow-core☕io.undertow:undertow-coreReal-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
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | io.undertow:undertow-core | ≥ 2.1.0&&< 2.1.5 | 2.1.5io.undertow:undertow-core:2.1.5 |
| ☕Maven | io.undertow:undertow-core | all versions | 2.0.33io.undertow:undertow-core:2.0.33 |
Affected Products
jboss fuseredhatopenshift application runtimesredhatundertowredhatDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for io.undertow:undertow-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update io.undertow:undertow-core to 2.1.5 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-27782 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
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.
The issue can be mitigated by using HTTP/1.1 instead of AJP to proxy to the back-end.Source: Red Hat security advisory for CVE-2020-27782 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Fuse 7.10 | undertow | RHSA-2021:5134 |
| Red Hat Integration | undertow | RHSA-2021:3205 |
| Red Hat Integration Camel Quarkus 2 | see advisory | RHSA-2021:3207 |
| Red Hat JBoss Enterprise Application Platform 7 | undertow-core | RHSA-2021:0250 |
| Red Hat JBoss Enterprise Application Platform 7.1 EUS for RHEL 7 | eap7-glassfish-el-0:3.0.1-4.b08_redhat_00005.1.ep7.el7 | RHSA-2025:9582 |
| Red Hat JBoss Enterprise Application Platform 7.3 for RHEL 6 | eap7-activemq-artemis-0:2.9.0-7.redhat_00017.1.el6eap | RHSA-2021:0246 |
| Red Hat JBoss Enterprise Application Platform 7.3 for RHEL 7 | eap7-activemq-artemis-0:2.9.0-7.redhat_00017.1.el7eap | RHSA-2021:0247 |
| Red Hat JBoss Enterprise Application Platform 7.3 for RHEL 8 | eap7-activemq-artemis-0:2.9.0-7.redhat_00017.1.el8eap | RHSA-2021:0248 |
Frequently Asked Questions
Is CVE-2020-27782 in your dependencies?
Find it across Maven, including transitive dependencies.