---
title: "CVE-2026-52863\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-2026-52863?format=md
keywords: index, follow
---

# CVE-2026-52863

Publication date 22 July 2026

Last updated 6 August 2026

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**5.9 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2026-52863?format=md#impact-score)

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## Description

In NLnet Labs Unbound 1.25.0 up to and including 1.25.1, a fix that makes
the 'respip' and 'dns64' modules work together, creates a shallow copy of
the view name in effect that could lead to memory corruption if the owner
of the original view name is jostled out when Unbound is under pressure.
Unbound needs to be configured with one of 'respip'/'rpz' modules, together
with a module that can attach subqueries (respip CNAME redirection, dns64,
subnetcache) and a configured 'access-control-view' while Unbound is under
pressure so that joslte logic kicks in and starts dropping slow queries.
The subquery is getting a shallow copy of the view name and if the super
query which owns the view name is jostled out, memory corruption can occur.
Likelihood of a crash is low, since it relies heavily on the underlying
memory allocator and the memory layout. Debug memory builds (e.g., ASAN)
that catch the free terminate the server.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| unbound | 26.04 LTS resolute | Needs evaluation |
| 24.04 LTS noble | Needs evaluation |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | Needs evaluation |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Needs evaluation |
| 14.04 LTS trusty | 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)

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

5.9 · Medium

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 5.9 · Medium |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-52863)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-52863)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-52863)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-52863)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-52863>
* <https://community.nlnetlabs.nl/t/unbound-1-25-2-released/3430>