CVE-2020-27782

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.

Published: 2021-02-23 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]

NVD Status：Modified，CVE State: published

View at NVD, CVE.org, EUVD

Threat Intelligence & Risk Assessment for CVE-2020-27782

EPSS CVSS CWE GHSA Affected OS Tracker

Conclusion & alert: CVE-2020-27782 is rated Moderate Risk (54.1/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.27%). Core evidence: EPSS rose +1.09% over the last day, indicating growing attacker interest. Mandatory action: Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2020-27782

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.18%	1.27%	+1.09%
2	2025-11-21	0.31%	0.18%	-0.13%
3	2025-03-30	—	0.31%	—

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-27782

CVSS metrics for this CVE.

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
7.5	3.1	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:N) Could be attacked over the internet or any normal routed network—not just someone sitting at the machine. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	3.9	3.6	[email protected]
7.8	2.0	HIGH	`AV:N/AC:L/Au:N/C:N/I:N/A:C` Click to expand Access vector (AV:N) Can be exploited remotely over network reachability. Access complexity (AC:L) Exploitation conditions are straightforward and predictable. Authentication (AU:N) No authentication is required. Confidentiality impact (C:N) No confidentiality impact. Integrity impact (I:N) No integrity impact. Availability impact (A:C) Complete availability impact.	10.0	6.9	[email protected]

Weakness enumeration for CVE-2020-27782

CWE-400 MITRE ↗

GitHub Security Advisory for CVE-2020-27782

GHSA-rhcw-wjcm-9h6g · Severity: high · Ecosystem: maven — Denial of service in Undertow

OS Trackers for CVE-2020-27782

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2020-27782 not yet assigned priority: Debian including 1 source packages (undertow), 2 status rows across 2 suites (forky, sid): resolved 2.	https://security-tracker.debian.org/tracker/CVE-2020-27782
`redhat`	high	—	https://access.redhat.com/security/cve/CVE-2020-27782
`ubuntu`	medium	CVE-2020-27782 medium priority: Ubuntu including 1 source packages (undertow), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): needs-triage 7, ignored 6, DNE 3.	https://ubuntu.com/security/CVE-2020-27782

Affected software / configurations for CVE-2020-27782

Vendor	Product	Version	Raw CPE
redhat	jboss_fuse	6.0.0	cpe:2.3:a:redhat:jboss_fuse:6.0.0:::::::*
redhat	jboss_fuse	7.0.0	cpe:2.3:a:redhat:jboss_fuse:7.0.0:::::::*
redhat	openshift_application_runtimes	—	cpe:2.3:a:redhat:openshift_application_runtimes:-:::::::*
redhat	undertow	2.0.33	cpe:2.3:a:redhat:undertow:2.0.33:sp2::::::
redhat	undertow	2.1.5	cpe:2.3:a:redhat:undertow:2.1.5:sp1::::::
redhat	undertow	2.2.3	cpe:2.3:a:redhat:undertow:2.2.3:sp1::::::

References for CVE-2020-27782

URL	Tags
https://bugzilla.redhat.com/show_bug.cgi?id=1901304	Issue Tracking Vendor Advisory

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