CVE-2020-36320Public exploitNetwork attack vector

Application hang via exponential email regex backtracking

Published Apr 23, 2021 · Updated Sep 16, 2024

Regular expression denial of service in Vaadin 7.0.0 through 7.7.21 allows remote attackers to hang applications via crafted email input. EmailValidator applies a nested-quantifier validation pattern to attacker-controlled addresses, causing exponential backtracking on crafted failures. Any reachable Vaadin email field using server-side validation is sufficient; repeated submissions can occupy the UI thread pool and leave the application unresponsive.

CVSS severity7.5
High
EPSS probability1.96%
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 7.0.0 through 7.7.21 allows remote attackers to hang applications via crafted email input. EmailValidator applies a nested-quantifier validation pattern to attacker-controlled addresses, causing exponential backtracking on crafted failures. Any reachable Vaadin email field using server-side validation is sufficient; repeated submissions can occupy the UI thread pool and leave the application unresponsive.

The record

CVE
CVE-2020-36320
Published
Apr 23, 2021
Updated
Sep 16, 2024
Vendor
Vaadin
Product
Vaadin Framework
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 16, 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=7.0.0 <*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vaadin · Vaadin Frameworkversion=7.0.0 <*
Vaadin · Vaadin Serverversion=7.0.0 <*

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.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

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Technologies

Your stack

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Your stack

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