CVE-2021-3859

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.

Published: 2022-08-26 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-3859 is rated Moderate Risk (47.6/100): CVSS High severity, with medium exploitation likelihood (EPSS 0.29%). 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-2021-3859

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 2026-01-05 0.90% 0.29% -0.61%
2 2026-01-04 0.81% 0.90% +0.09%
3 2026-01-03 — 0.81% —

Full EPSS history (20 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-3859

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]

Weakness enumeration for CVE-2021-3859

GitHub Security Advisory for CVE-2021-3859

GHSA-339q-62wm-c39w · Severity: high · Ecosystem: maven — Undertow vulnerable to Denial of Service (DoS) attacks

OS Trackers for CVE-2021-3859

vendor priority summary link
debian not yet assigned CVE-2021-3859 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-2021-3859
redhat high — https://access.redhat.com/security/cve/CVE-2021-3859
ubuntu medium CVE-2021-3859 medium priority: Ubuntu including 1 source packages (undertow), 14 status rows across 14 suites (bionic, focal, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): needs-triage 7, ignored 5, DNE 2. https://ubuntu.com/security/CVE-2021-3859

Affected software / configurations for CVE-2021-3859

Vendor Product Version Raw CPE
redhat jboss_enterprise_application_platform 7.3 cpe:2.3:a:redhat:jboss_enterprise_application_platform:7.3:*:*:*:*:*:*:*
redhat jboss_enterprise_application_platform 7.4 cpe:2.3:a:redhat:jboss_enterprise_application_platform:7.4:*:*:*:*:*:*:*
redhat single_sign-on 7.4.10 cpe:2.3:a:redhat:single_sign-on:7.4.10:*:*:*:*:*:*:*
redhat single_sign-on 7.5.1 cpe:2.3:a:redhat:single_sign-on:7.5.1:*:*:*:*:*:*:*
redhat undertow < 2.2.15 cpe:2.3:a:redhat:undertow:*:*:*:*:*:*:*:*
netapp cloud_secure_agent — cpe:2.3:a:netapp:cloud_secure_agent:-:*:*:*:*:*:*:*
netapp oncommand_insight — cpe:2.3:a:netapp:oncommand_insight:-:*:*:*:*:*:*:*
netapp oncommand_workflow_automation — cpe:2.3:a:netapp:oncommand_workflow_automation:-:*:*:*:*:*:*:*

References for CVE-2021-3859

cvelogic Threat Intelligence