---
title: "CVE-2026-5545\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-2026-5545?format=md
keywords: index, follow
---

# CVE-2026-5545

Publication date 29 April 2026

Last updated 10 July 2026

---

Ubuntu priority

**Medium**

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

## Cvss 3 Severity Score

**6.5 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2026-5545?format=md#impact-score)

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## Description

libcurl might in some circumstances reuse the wrong connection when asked
to
do an authenticated HTTP(S) request after a Negotiate-authenticated one,
when
both use the same host.
libcurl features a pool of recent connections so that subsequent requests
can
reuse an existing connection to avoid overhead.
When reusing a connection a range of criteria must be met. Due to a logical
error in the code, a request that was issued by an application could
wrongfully reuse an existing connection to the same server that was
authenticated using different credentials.
An application that first uses Negotiate authentication to a server with
`user1:password1` and then does another operation to the same server asking
for any authentication method but for `user2:password2` (while the previous
connection is still alive) - the second request gets confused and wrongly
reuses the same connection and sends the new request over that connection
thinking it uses a mix of user1's and user2's credentials when it is in
fact
still using the connection authenticated for user1...

[Read the notes from the security team](https://ubuntu.com/security/CVE-2026-5545?format=md#notes)

## Mitigation

Avoid using HTTP Negotiate in your application

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| curl | 26.04 LTS resolute | Fixed 8.18.0-1ubuntu2.1 |
| 25.10 questing | Fixed 8.14.1-2ubuntu1.3 |
| 24.04 LTS noble | Fixed 8.5.0-2ubuntu10.9 |
| 22.04 LTS jammy | Fixed 7.81.0-1ubuntu1.24 |
| 20.04 LTS focal | Fixed 7.68.0-1ubuntu2.25+esm5  Ubuntu Pro |
| 18.04 LTS bionic | Not affected |
| 16.04 LTS xenial | Not affected |
| 14.04 LTS trusty | Not affected |

---

* [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-2026-5545?format=md#patch-details)

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## Notes

---

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

Introduced-in: https://github.com/curl/curl/commit/e56ae1426c

### 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 |
| --- | --- |
| curl | * Upstream:   [33e4398](https://github.com/curl/curl/commit/33e43985b8f3b9e6669) |

## Severity score breakdown

CVSS version:
CVSS v3.0

**Base score**

6.5 · Medium

* Base metrics

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

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.5 · Medium |
  | Exploitability score | - |
  | Impact score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-5545)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-5545)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-5545)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-5545)

### Related Ubuntu Security Notices (USN)

+ [USN-8227-1](https://usn.ubuntu.com/USN-8227-1)
+ curl vulnerabilities
+ 4 May 2026

+ [USN-8525-1](https://usn.ubuntu.com/USN-8525-1)
+ curl vulnerabilities
+ 9 July 2026

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-5545>
* <https://curl.se/docs/CVE-2026-5545.html>