USN-8227-1: curl vulnerabilities

Publication date

4 May 2026

Overview

curl could be made to expose sensitive information over the network.


Packages

  • curl - HTTP, HTTPS, and FTP client and client libraries

Details

It was discovered that curl incorrectly reused non-TLS connections when
TLS was required in some STARTTLS configurations. A remote attacker could
possibly use this issue to obtain sensitive information. (CVE-2026-4873)

It was discovered that curl incorrectly reused certain HTTP Negotiate
connections. A remote attacker could possibly use this issue to obtain
sensitive information. (CVE-2026-5545)

It was discovered that curl incorrectly reused certain SMB connections. A
remote attacker could possibly use this issue to obtain sensitive
information. (CVE-2026-5773)

It was discovered that curl could leak proxy credentials when handling
redirects in some configurations. A remote attacker could possibly use
this issue to obtain sensitive information. (CVE-2026-6253)

It was...

It was discovered that curl incorrectly reused non-TLS connections when
TLS was required in some STARTTLS configurations. A remote attacker could
possibly use this issue to obtain sensitive information. (CVE-2026-4873)

It was discovered that curl incorrectly reused certain HTTP Negotiate
connections. A remote attacker could possibly use this issue to obtain
sensitive information. (CVE-2026-5545)

It was discovered that curl incorrectly reused certain SMB connections. A
remote attacker could possibly use this issue to obtain sensitive
information. (CVE-2026-5773)

It was discovered that curl could leak proxy credentials when handling
redirects in some configurations. A remote attacker could possibly use
this issue to obtain sensitive information. (CVE-2026-6253)

It was discovered that curl could leak cookies because of stale custom
cookie host handling in some requests. A remote attacker could possibly
use this issue to obtain sensitive information. (CVE-2026-6276)

It was discovered that curl could leak .netrc credentials when reusing
proxy connections in some situations. A remote attacker could possibly use
this issue to obtain sensitive information. (CVE-2026-6429)

It was discovered that curl could leak Digest authentication state when
switching proxies in some situations. A remote attacker could possibly use
this issue to obtain sensitive information. (CVE-2026-7168)


Update instructions

In general, a standard system update will make all the necessary changes.

Learn more about how to get the fixes.

The problem can be corrected by updating your system to the following package versions:


Reduce your security exposure

Ubuntu Pro provides ten-year security coverage to 25,000+ packages in Main and Universe repositories, and it is free for up to five machines.


Have additional questions?

Talk to a member of the team ›