# CVE-2024-5971: Undertow: response write hangs in case of java 17 tlsv1.3 newsessionticket

> Undertow fails to terminate chunked responses in Java 17 TLSv1.3, causing clients to hang and leading to server-side resource exhaustion and denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Jul 2024
- **Updated:** 4 Sep 2026
- **Also known as:** CLSA-2026-1775435425, DEBIAN-CVE-2024-5971, GHSA-xpp6-8r3j-ww43, UBUNTU-CVE-2024-5971

## What is CVE-2024-5971?

CVE-2024-5971 is a high-severity denial of service vulnerability in Red Hat Build of Keycloak, published on 8 Jul 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability was found in Undertow, where the chunked response hangs after the body was flushed. The response headers and body were sent but the client would continue waiting as Undertow does not send the expected 0\r\n termination of the chunked response. This results in uncontrolled resource consumption, leaving the server side to a denial of service attack. This happens only with Java 17 TLSv1.3 scenarios.

Weakness: CWE-674 (Uncontrolled Recursion)

## Which versions are affected by CVE-2024-5971?

4 open source packages ship an affected version, including io.undertow:undertow-core.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `io.undertow:undertow-core` | Maven | All versions | 2.2.34.Final |
| `io.undertow:undertow-core` | Maven | All versions | 2.2.34.Final |
| `io.undertow:undertow-core` | Maven | From 2.3.0.Alpha1 | 2.3.15.Final |
| `io.undertow:undertow-core` | Maven | From 2.3.0.Alpha1 | 2.3.15.Final |

## How do I fix CVE-2024-5971?

Upgrade io.undertow:undertow-core to a fixed version for your release line: 2.2.34.Final or 2.3.15.Final.

## Is CVE-2024-5971 being exploited?

There is no known exploitation of CVE-2024-5971 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-5971 and fix it if it is affected.

What it is: CVE-2024-5971 is a high-severity denial of service vulnerability in Red Hat Build of Keycloak, published on 8 Jul 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2024-5971 in the wild and no public exploit code.

Affected packages and fixed versions:
- io.undertow:undertow-core (Maven): affected all versions; fixed in 2.2.34.Final
- io.undertow:undertow-core (Maven): affected all versions; fixed in 2.2.34.Final
- io.undertow:undertow-core (Maven): affected from 2.3.0.Alpha1; fixed in 2.3.15.Final
- io.undertow:undertow-core (Maven): affected from 2.3.0.Alpha1; fixed in 2.3.15.Final

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2024-5971/ (Markdown: https://insights.sbomify.com/CVE-2024-5971/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-5971
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-5971
- OSV: https://osv.dev/vulnerability/CVE-2024-5971

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-5971/
Summaries are generated and may contain mistakes; the official description above is the record.