---
title: "CVE-2026-34829\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2026-34829?format=md
keywords: index, follow
---

# CVE-2026-34829

Publication date 2 April 2026

Last updated 23 April 2026

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**7.5 · High**

[Score breakdown](https://ubuntu.com/security/CVE-2026-34829?format=md#impact-score)

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## Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23,
3.1.21, and 3.2.6, Rack::Multipart::Parser only wraps the request body in a
BoundedIO when CONTENT\_LENGTH is present. When a multipart/form-data
request is sent without a Content-Length header, such as with HTTP chunked
transfer encoding, multipart parsing continues until end-of-stream with no
total size limit. For file parts, the uploaded body is written directly to
a temporary file on disk rather than being constrained by the buffered
in-memory upload limit. An unauthenticated attacker can therefore stream an
arbitrarily large multipart file upload and consume unbounded disk space.
This results in a denial of service condition for Rack applications that
accept multipart form data. This issue has been patched in versions 2.2.23,
3.1.21, and 3.2.6.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| ruby-rack | 26.04 LTS resolute | Vulnerable |
| 25.10 questing | Fixed 3.1.16-0.1ubuntu0.3 |
| 24.04 LTS noble | Fixed 2.2.7-1ubuntu0.7 |
| 22.04 LTS jammy | Fixed 2.1.4-5ubuntu1.2+esm3  Ubuntu Pro |
| 20.04 LTS focal | Fixed 2.0.7-2ubuntu0.1+esm10  Ubuntu Pro |
| 18.04 LTS bionic | Ignored changes too intrusive |
| 16.04 LTS xenial | Ignored end of ESM support, was ignored [changes too intrusive] |
| 14.04 LTS trusty | Ignored changes too intrusive |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)
* [Patch details](https://ubuntu.com/security/CVE-2026-34829?format=md#patch-details)

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### Patch details

For informational purposes only. We recommend not to cherry-pick updates. [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)

| Package | Patch details |
| --- | --- |
| ruby-rack | * Upstream:   [b3e5945](https://github.com/rack/rack/commit/b3e5945c648c5a5b6982e5072b26e51990991229) |

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

7.5 · High

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Privileges required | None |
  | User interaction | None |
  | Scope | Unchanged |
  | Confidentiality impact | None |
  | Integrity impact | None |
  | Availability impact | High |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 7.5 · High |
  | Exploitability score | - |
  | Impact score | - |

**Vector:** CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-34829)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-34829)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-34829)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-34829)

### Related Ubuntu Security Notices (USN)

+ [USN-8182-1](https://usn.ubuntu.com/USN-8182-1)
+ Rack vulnerabilities
+ 17 April 2026

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-34829>
* <https://github.com/rack/rack/security/advisories/GHSA-8vqr-qjwx-82mw>