---
title: "CVE-2026-5950\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-2026-5950?format=md
keywords: index, follow
---

# CVE-2026-5950

Publication date 20 May 2026

Last updated 27 May 2026

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**5.3 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2026-5950?format=md#impact-score)

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## Description

An unbounded resend loop vulnerability exists in the BIND 9 resolver state
machine during bad-server handling, enabling a remote unauthenticated
attacker to cause severe resource exhaustion by sending queries that
trigger specific retry conditions.
This issue affects BIND 9 versions 9.18.36 through 9.18.48, 9.20.8 through
9.20.22, 9.21.7 through 9.21.21, 9.18.36-S1 through 9.18.48-S1, and
9.20.9-S1 through 9.20.22-S1.

[Read the notes from the security team](https://ubuntu.com/security/CVE-2026-5950?format=md#notes)

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| bind9 | 26.04 LTS resolute | Fixed 1:9.20.18-1ubuntu2.1 |
| 25.10 questing | Fixed 1:9.20.11-1ubuntu2.4 |
| 24.04 LTS noble | Fixed 1:9.18.39-0ubuntu0.24.04.5 |
| 22.04 LTS jammy | Fixed 1:9.18.39-0ubuntu0.22.04.4 |
| 20.04 LTS focal | Not affected |
| 18.04 LTS bionic | Not affected |
| 16.04 LTS xenial | Not affected |
| 14.04 LTS trusty | Not affected |
| isc-dhcp | 26.04 LTS resolute | Needs evaluation |
| 25.10 questing | Ignored end of life, was needs-triage |
| 24.04 LTS noble | Needs evaluation |
| 22.04 LTS jammy | Not affected |
| 20.04 LTS focal | Not affected |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Not affected |
| 14.04 LTS trusty | Not affected |
| bind9-libs | 26.04 LTS resolute | Not in release |
| 25.10 questing | Not in release |
| 24.04 LTS noble | Not in release |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | 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-2026-5950?format=md#patch-details)

## Notes

---

### [alexmurray](https://launchpad.net/~alexmurray)

As of isc-dhcp-4.4.3-1, isc-dhcp vendors bind9 libs

---

### [mdeslaur](https://launchpad.net/~mdeslaur)

in focal and jammy, isc-dhcp uses the bind9-libs package
This is unlikely to affect isc-dhcp's use of bind9-libs and the
vendored bind9 libs, marking as negligible

### 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 |
| --- | --- |
| bind9 | * Upstream:   [1c390aa](https://gitlab.isc.org/isc-projects/bind9/-/commit/1c390aacaedaf788a04ba053758c1b7f53673f0b) * Upstream:   [43d1737](https://gitlab.isc.org/isc-projects/bind9/-/commit/43d173797e3c781c7e38d879c3c765f01cc09c59) |

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

5.3 · Medium

* 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 | Low |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 5.3 · Medium |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-5950)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-5950)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-5950)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-5950)

### Related Ubuntu Security Notices (USN)

+ [USN-8293-1](https://usn.ubuntu.com/USN-8293-1)
+ Bind vulnerabilities
+ 21 May 2026

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-5950>
* <https://kb.isc.org/docs/cve-2026-5950>