CVE-2021-31405Network attack vector

Denial of service via EmailField regex backtracking

Published Apr 23, 2021 · Updated Sep 17, 2024

Regular expression denial of service in Vaadin EmailField allows remote attackers to hang server UI threads with malicious addresses. The server-side com.vaadin.flow.component.textfield.EmailField validation pattern performs exponential backtracking on attacker-controlled email input. No authentication or user interaction is required; submitting or blurring a crafted field can indefinitely occupy UI threads and exhaust the thread pool, leaving the application unresponsive.

CVSS severity7.5
High
EPSS probability1.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Vaadin EmailField allows remote attackers to hang server UI threads with malicious addresses. The server-side com.vaadin.flow.component.textfield.EmailField validation pattern performs exponential backtracking on attacker-controlled email input. No authentication or user interaction is required; submitting or blurring a crafted field can indefinitely occupy UI threads and exhaust the thread pool, leaving the application unresponsive.

The record

CVE
CVE-2021-31405
Published
Apr 23, 2021
Updated
Sep 17, 2024
Vendor
Vaadin
Product
Vaadin Text Field Flow
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 23, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 17, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=2.0.4 <* changes=[{"at":"3.0.0","status":"affected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vaadin · Vaadin Text Field Flowversion=2.0.4 <* changes=[{"at":"3.0.0","status":"affected"}]
Vaadin · Vaadin Frameworkversion=14.0.6 <* changes=[{"at":"15.0.0","status":"affected"}]

Published CVSS scores

7.5VaadinCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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