CVE-2021-3597: undertow-core Race Condition Vulnerability
Summary
CVE-2021-3597: undertow Race Condition vulnerability. Affects io.undertow:undertow-core across 2 version ranges.
< 2.0.39.Final
>= 2.1.0, < 2.2.9.Final
Fixed in 2.0.39.Final or 2.2.9.Final, depending on the release line you run. How to fix ↓
Also tracked for
- undertow · Debian:13
The same CVE-2021-3597 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
undertow-core is a Java web server that provides a lightweight and high-performance foundation for building web applications. It is widely used in various Java-based frameworks and applications. This vulnerability affects versions of undertow-core prior to 2.0.35.SP1, 2.2.6.SP1, 2.2.7.SP1, 2.0.36.SP1, 2.2.9.Final, and 2.0.39.Final.
Vulnerability Detail
The vulnerability identified as CVE-2021-3597 is a race condition flaw in undertow-core's HTTP2SourceChannel. Under certain circumstances, the final frame fails to be written, leading to a denial of service (DoS) condition. The primary impact of this vulnerability is on the availability of affected systems. The Common Vulnerability Scoring System (CVSS) score for this vulnerability is 5.9.
How To Fix
Latest published version: 2.4.4.Final as of 23 Oct 2026
Upgrading to it may include breaking changes; the versions below are the minimum fixed release for this vulnerability.
If you can't move to the latest
The minimum fixed version depends on the release line you run.
-
< 2.0.39.Final2.0.39.Final -
>= 2.1.0, < 2.2.9.Final2.2.9.Final
Tip — Not sure which release line you're on? Vulert can find the fix for the version you are using. Scan free →
Workaround
No specific workaround has been provided for this vulnerability.
Conclusion
The undertow-core Race Condition vulnerability (CVE-2021-3597) can lead to a denial of service (DoS) condition in affected systems. It is recommended to upgrade to the fixed versions mentioned earlier to mitigate this vulnerability. For further assistance and support in vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for io.undertow:undertow-core →
FAQ
The vulnerability can result in a denial of service (DoS) condition, impacting the availability of affected systems.
Versions prior to 2.0.35.SP1, 2.2.6.SP1, 2.2.7.SP1, 2.0.36.SP1, 2.2.9.Final, and 2.0.39.Final are affected.
The CVSS score for this vulnerability is 5.9, indicating a moderate severity.
To fix this vulnerability, upgrade undertow-core to version 2.2.9.Final or 2.0.39.Final, depending on the currently used version.
No specific workaround has been provided for this vulnerability.
Related vulnerabilities
Recent vulnerabilities recorded for io.undertow:undertow-core.
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