Sign in
Deutsch English Español Polski
Medium

HTTP Request Smuggling in Undertow

  • Disclosed: 30.04.2021
  • Updated: 11.10.2026 11:22

A flaw was discovered in all versions of Undertow before Undertow 2.2.0.Final, where HTTP request smuggling related to CVE-2017-2666 is possible against HTTP/1.x and HTTP/2 due to permitting invalid characters in an HTTP request. This flaw allows an attacker to poison a web-cache, perform an XSS attack, or obtain sensitive information from request other than their own.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Java / Kotlin (Maven) io.undertow:undertow-core < 2.2.0.Final 2.2.0.Final

References

CVSS score 4.8/10
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness (CWE)
CWE-444
Platform
Java / Kotlin (Maven)
Package
io.undertow:undertow-core
Disclosed
30.04.2021
Updated
11.10.2026 11:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-p9w3-gwc2-cr49 - CC BY 4.0

Vulnerability history: io.undertow:undertow-core

All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (39) in the archive
Total entries
39
First → latest
10.2018 03.2026
Without a fix
1
Exploited in attacks
0

Severity breakdown

  • Critical 4
  • High 19
  • Medium 16

Disclosures per year

Severity:
  1. HTTP Request Smuggling in Undertow this entry
    Medium · 4.8 CVE-2020-10687 < 2.2.0.Final 2.2.0.Final
  2. Undertow Servlets Vulnerable to Remote DoS via OutOfMemoryError when Passed Large Parameter Names
    High · 7.5 CVE-2024-4027 < 2.2.39.Final, >= 2.4.0.Alpha1, < 2.4.0.Beta1, >= 2.3.0.Alpha1, < 2.3.21.Final 2.2.39.Final, 2.4.0.Beta1, 2.3.21.Final
  3. Undertow HTTP server core doesn't properly validate the Host header in incoming HTTP requests
    Critical · 9.6 CVE-2025-12543 >= 2.3.0.Alpha1, < 2.3.21.Final, < 2.2.39.Final, = 2.4.0.Alpha1 2.3.21.Final, 2.2.39.Final
  4. Undertow OutOfMemory when parsing form data encoding with application/x-www-form-urlencoded
    High · 7.5 CVE-2024-3884 < 2.2.39.Final, >= 2.4.0.Alpha1, < 2.4.0.Beta1, >= 2.3.0.Alpha1, < 2.3.21.Final 2.2.39.Final, 2.4.0.Beta1, 2.3.21.Final
  5. Undertow MadeYouReset HTTP/2 DDoS Vulnerability
    High · 7.5 CVE-2025-9784 < 2.2.38.Final, >= 2.3.0.Alpha1, < 2.3.20.Final 2.2.38.Final, 2.3.20.Final
  6. Undertow incorrectly parses cookies
    High · 7.4 CVE-2023-4639 >= 2.3.0.Alpha1, < 2.3.11.Final, < 2.2.30.Final 2.3.11.Final, 2.2.30.Final
  7. Undertow vulnerable to Race Condition
    High · 7.5 CVE-2024-7885 < 2.2.36.Final, >= 2.3.0.Alpha1, < 2.3.17.Final 2.2.36.Final, 2.3.17.Final
  8. Undertow Denial of Service vulnerability
    High · 7.5 CVE-2024-5971 >= 2.3.0.Alpha1, < 2.3.15.Final, < 2.2.34.Final 2.3.15.Final, 2.2.34.Final
  9. Undertow's url-encoded request path information can be broken on ajp-listener
    High · 7.5 CVE-2024-6162 >= 2.3.0.Alpha1, < 2.3.14.Final, < 2.2.33.Final 2.3.14.Final, 2.2.33.Final
  10. Undertow Uncontrolled Resource Consumption Vulnerability
    High · 7.5 CVE-2024-1635 >= 2.3.0.Final, < 2.3.12.Final, < 2.2.31.Final 2.3.12.Final, 2.2.31.Final
  11. Undertow denial of service vulnerability
    High · 7.5 CVE-2023-1108 >= 2.3.0, < 2.3.5.Final, < 2.2.24.Final 2.3.5.Final, 2.2.24.Final
  12. Undertow client not checking server identity presented by server certificate in https connections
    Critical · 9.8 CVE-2022-4492 >= 2.3.0, < 2.3.5.Final, < 2.2.24.Final 2.3.5.Final, 2.2.24.Final
  13. Undertow vulnerable to Dos via Large AJP request
    High · 7.5 CVE-2022-2053 < 2.2.19.Final, >= 2.3.0.Alpha1, < 2.3.0.Alpha2 2.2.19.Final, 2.3.0.Alpha2
  14. Undertow vulnerable to Denial of Service (DoS) attacks
    High · 7.5 CVE-2021-3859 < 2.2.15 2.2.15
  15. Undertow vulnerable to memory exhaustion due to buffer leak
    High · 7.5 CVE-2021-3690 < 2.0.40, >= 2.2.0, < 2.2.10 2.0.40, 2.2.10
  16. Undertow Uncontrolled Resource Consumption
    High · 7.5 CVE-2021-3629 < 2.0.40.Final, >= 2.1.0, < 2.2.11.Final 2.0.40.Final, 2.2.11.Final
  17. Improper Authorization in Undertoe
    High · 8.6 CVE-2020-1745 < 2.0.30 2.0.30
  18. Improper Input Validation in Undertow
    High · 8.1 CVE-2020-1757 < 2.1.0 2.1.0
  19. Undertow vulnerable to Uncontrolled Resource Consumption
    High · 7.5 CVE-2019-14888 < 2.0.29.Final 2.0.29.Final
  20. Undertow Request Smuggling vulnerability
    High · 7.5 CVE-2017-12165 < 1.3.31, >= 1.4.0, < 1.4.17, >= 2.0.0.Alpha1, < 2.0.0.Beta1 1.3.31, 1.4.17, 2.0.0.Beta1
  21. Denial of service in Undertow
    High · 7.5 CVE-2020-27782 >= 2.1.0, < 2.1.5, < 2.0.33 2.1.5, 2.0.33
Show more (3) Showing 21 of 24

Know which vulnerabilities affect your application

With the DockRay integration and software inventory enabled, DockRay checks reported component versions against known vulnerabilities and notifies you about confirmed matches. Coverage depends on the supported technology and available advisory data.

Connect your application
DockRay newsletter

Application security in your inbox

Important vulnerabilities, actionable guidance and practical advice for your applications. Choose your technologies and follow what matters to your project.

  • A daily digest of new vulnerabilities, critical ones included.
  • Notifications about important updates.
  • Practical advice on application security and monitoring.

Leave empty to receive updates for every technology.

Privacy policy

Free to subscribe. Unsubscribe with one click in any email.