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High

Undertow vulnerable to Dos via Large AJP request

  • Disclosed: 06.08.2022
  • Updated: 11.10.2026 11:21

When a POST request comes through AJP and the request exceeds the max-post-size limit (maxEntitySize), Undertow's AjpServerRequestConduit implementation closes a connection without sending any response to the client/proxy. This behavior results in that a front-end proxy marking the backend worker (application server) as an error state and not forward requests to the worker for a while. In mod_cluster, this continues until the next STATUS request (10 seconds intervals) from the application server updates the server state. So, in the worst case, it can result in "All workers are in error state" and mod_cluster responds "503 Service Unavailable" for a while (up to 10 seconds). In mod_proxy_balancer, it does not forward requests to the worker until the "retry" timeout passes. However, luckily, mod_proxy_balancer has "forcerecovery" setting (On by default; this parameter can force the immediate recovery of all workers without considering the retry parameter of the workers if all workers of a balancer are in error state.). So, unlike mod_cluster, mod_proxy_balancer does not result in responding "503 Service Unavailable". An attacker could use this behavior to send a malicious request and trigger server errors, resulting in DoS (denial of service). This flaw was fixed in Undertow 2.2.19.Final, Undertow 2.3.0.Alpha2.

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Java / Kotlin (Maven) io.undertow:undertow-core < 2.2.19.Final, >= 2.3.0.Alpha1, < 2.3.0.Alpha2 2.2.19.Final, 2.3.0.Alpha2

References

CVSS score 7.5/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE)
CWE-400
Platform
Java / Kotlin (Maven)
Package
io.undertow:undertow-core
Disclosed
06.08.2022
Updated
11.10.2026 11:21

Sources and licenses

OSV / GitHub Advisory Database - GHSA-95rf-557x-44g5 - 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. 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
  2. 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
  3. 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
  4. 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
  5. 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
  6. 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
  7. 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
  8. 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
  9. 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
  10. 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
  11. 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
  12. Undertow vulnerable to Dos via Large AJP request this entry
    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
  13. Undertow vulnerable to Denial of Service (DoS) attacks
    High · 7.5 CVE-2021-3859 < 2.2.15 2.2.15
  14. 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
  15. 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
  16. Improper Authorization in Undertoe
    High · 8.6 CVE-2020-1745 < 2.0.30 2.0.30
  17. Improper Input Validation in Undertow
    High · 8.1 CVE-2020-1757 < 2.1.0 2.1.0
  18. Undertow vulnerable to Uncontrolled Resource Consumption
    High · 7.5 CVE-2019-14888 < 2.0.29.Final 2.0.29.Final
  19. 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
  20. 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 20 of 23

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