CVE-2017-20190Public exploit

Client-side slowdown via stacked Unicode combining characters

Published Mar 26, 2024 · Updated Aug 8, 2024

Denial of service in Microsoft Windows 8 through 11 allows context-dependent attackers to cause temporary client-side slowdown via Zalgo text. Affected text-rendering technologies spend excessive computation processing strings containing many stacked Unicode combining characters, degrading interface responsiveness. The record identifies neither a specific component nor a delivery path, and the classification is disputed because the input is valid Unicode.

CVSS severityUnavailable
Unscored
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Microsoft Windows 8 through 11 allows context-dependent attackers to cause temporary client-side slowdown via Zalgo text. Affected text-rendering technologies spend excessive computation processing strings containing many stacked Unicode combining characters, degrading interface responsiveness. The record identifies neither a specific component nor a delivery path, and the classification is disputed because the input is valid Unicode.

The record

CVE
CVE-2017-20190
Published
Mar 26, 2024
Updated
Aug 8, 2024
Vendor
Microsoft
Product
Windows
Classifications
CWE-176, T1499
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Mar 26, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 8, 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=8 <=11

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

Microsoft · Windowsversion=8 <=11

Published CVSS scores

No CVSS assessment is available in this record.

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

Weakness, pattern, technique

CWE-176Improper Handling of Unicode Encoding
T1499Endpoint Denial of Service

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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