CVE-2019-17569Network attack vector

Request smuggling via invalid Transfer-Encoding token parsing

Published Feb 24, 2020 · Updated Aug 5, 2024

HTTP request smuggling in affected Apache Tomcat releases allows remote attackers to desynchronize requests via malformed Transfer-Encoding headers. The parseTokenList regression accepts invalid Transfer-Encoding token lists instead of rejecting the request, creating divergent message boundaries. Exposure requires a reverse proxy that handles the same invalid header differently and Tomcat 7.0.98 through 7.0.99, 8.5.48 through 8.5.50, or 9.0.28 through 9.0.30.

CVSS severity4.8
Medium
EPSS probability8.87%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP request smuggling in affected Apache Tomcat releases allows remote attackers to desynchronize requests via malformed Transfer-Encoding headers. The parseTokenList regression accepts invalid Transfer-Encoding token lists instead of rejecting the request, creating divergent message boundaries. Exposure requires a reverse proxy that handles the same invalid header differently and Tomcat 7.0.98 through 7.0.99, 8.5.48 through 8.5.50, or 9.0.28 through 9.0.30.

The record

CVE
CVE-2019-17569
Published
Feb 24, 2020
Updated
Aug 5, 2024
Vendor
The Apache Software Foundation
Product
Apache Tomcat
Classifications
CWE-444, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 24, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 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=7.0.98 to 7.0.99
  2. Affected versionversion=8.5.48 to 8.5.50
  3. Affected versionversion=Apache Tomcat 9.0.28 to 9.0.30

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Apache Software Foundation · Apache Tomcatversion=7.0.98 to 7.0.99; version=8.5.48 to 8.5.50; version=Apache Tomcat 9.0.28 to 9.0.30

Published CVSS scores

4.8GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

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-444Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

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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