---
title: "CVE-2026-58055\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-2026-58055?format=md
keywords: index, follow
---

# CVE-2026-58055

Publication date 28 June 2026

Last updated 2 July 2026

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**5.4 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2026-58055?format=md#impact-score)

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## Description

nghttp2's nghttpx proxy through 1.69.0 forwards an HTTP/1.1 Upgrade request
that also carries a Content-Length header and body onto reusable keep-alive
backend connections, re-adding the Upgrade and Connection headers while
passing Content-Length verbatim. A backend that resolves the resulting
ambiguous message in the attacker's favor enables HTTP request/response
smuggling and cross-client response-queue poisoning.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| nghttp2 | 26.04 LTS resolute | Fixed 1.68.0-2ubuntu0.2 |
| 25.10 questing | Fixed 1.64.0-1.1ubuntu1.2 |
| 24.04 LTS noble | Fixed 1.59.0-1ubuntu0.4 |
| 22.04 LTS jammy | Fixed 1.43.0-1ubuntu0.4 |
| 20.04 LTS focal | Needs evaluation |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Needs evaluation |

---

* [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-2026-58055?format=md#patch-details)

### 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 |
| --- | --- |
| nghttp2 | * Upstream:   [ab28105](https://github.com/nghttp2/nghttp2/commit/ab28105c4a0197da24f8bfc414bc116055249e1e) |

## Severity score breakdown

CVSS version:

CVSS v4.0

[CVSS v4.0](https://ubuntu.com/security/CVE-2026-58055?format=md)
[CVSS v3.0](https://ubuntu.com/security/CVE-2026-58055?format=md)

**Base score**

6.3 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | High |
  | Attack requirements | None |
  | Privileges required | None |
  | User interaction | None |
  | Vulnerable system - Confidentiality impact | Low |
  | Vulnerable system - Integrity impact | Low |
  | Vulnerable system - Availability impact | None |
  | Subsequent system - Confidentiality impact | None |
  | Subsequent system - Integrity impact | Low |
  | Subsequent system - Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.3 · Medium |
  | Base + Threat score | - |
  | Base + Environmental score | - |
  | Base + Threat + Environmental score | - |

**Vector:** CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:L/SA:N

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-58055)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-58055)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-58055)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-58055)

### Related Ubuntu Security Notices (USN)

+ [USN-8495-1](https://usn.ubuntu.com/USN-8495-1)
+ nghttp2 vulnerability
+ 2 July 2026

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-58055>
* <https://github.com/bikini/exploitarium/tree/main/nghttp2-nghttpx-upgrade-queue-poison-poc>
* <https://www.vulncheck.com/advisories/nghttp2-nghttpx-http-request-response-smuggling-via-upgrade-request-with-content-length>