# CVE-2023-4639: Undertow: cookie smuggling/spoofing

> Attackers can exfiltrate HttpOnly cookies or spoof cookie values via malformed requests, leading to unauthorized data access or modification.

- **Severity:** High 7.4 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 17 Nov 2024
- **Updated:** 7 Feb 2025
- **Also known as:** CLSA-2026-1789372923, CLSA-2026-1789457514, DEBIAN-CVE-2023-4639, GHSA-3jrv-jgp8-45v3, UBUNTU-CVE-2023-4639

## What is CVE-2023-4639?

CVE-2023-4639 is a high-severity vulnerability in Red Hat Migration Toolkit for Applications 6, published on 17 Nov 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in Undertow, which incorrectly parses cookies with certain value-delimiting characters in incoming requests. This issue could allow an attacker to construct a cookie value to exfiltrate HttpOnly cookie values or spoof arbitrary additional cookie values, leading to unauthorized data access or modification. The main threat from this flaw impacts data confidentiality and integrity.

Weakness: CWE-444 (Inconsistent Interpretation of HTTP Requests)

## Which versions are affected by CVE-2023-4639?

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 | 2.2.30.Final |
| `io.undertow:undertow-core` | Maven | All versions | 2.2.30.Final |
| `io.undertow:undertow-core` | Maven | From 2.3.0.Alpha1 | 2.3.11.Final |
| `io.undertow:undertow-core` | Maven | From 2.3.0.Alpha1 | 2.3.11.Final |

## How do I fix CVE-2023-4639?

Upgrade io.undertow:undertow-core to a fixed version for your release line: 2.2.30.Final or 2.3.11.Final.

## Is CVE-2023-4639 being exploited?

There is no known exploitation of CVE-2023-4639 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-4639 and fix it if it is affected.

What it is: CVE-2023-4639 is a high-severity vulnerability in Red Hat Migration Toolkit for Applications 6, published on 17 Nov 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-2023-4639 in the wild and no public exploit code.

Affected packages and fixed versions:
- io.undertow:undertow-core (Maven): affected all versions; fixed in 2.2.30.Final
- io.undertow:undertow-core (Maven): affected all versions; fixed in 2.2.30.Final
- io.undertow:undertow-core (Maven): affected from 2.3.0.Alpha1; fixed in 2.3.11.Final
- io.undertow:undertow-core (Maven): affected from 2.3.0.Alpha1; fixed in 2.3.11.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-2023-4639/ (Markdown: https://insights.sbomify.com/CVE-2023-4639/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-4639
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-4639
- OSV: https://osv.dev/vulnerability/CVE-2023-4639

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-4639/
Summaries are generated and may contain mistakes; the official description above is the record.