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[USN-8227-1] curl vulnerabilities

Posted on 04 May 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8227-1
May 04, 2026

curl vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.04 LTS
- Ubuntu 25.10
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS

Summary:

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

Software Description:
- 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 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:

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

Ubuntu 26.04 LTS
curl 8.18.0-1ubuntu2.1
libcurl3t64-gnutls 8.18.0-1ubuntu2.1
libcurl4t64 8.18.0-1ubuntu2.1

Ubuntu 25.10
curl 8.14.1-2ubuntu1.3
libcurl3t64-gnutls 8.14.1-2ubuntu1.3
libcurl4t64 8.14.1-2ubuntu1.3

Ubuntu 24.04 LTS
curl 8.5.0-2ubuntu10.9
libcurl3t64-gnutls 8.5.0-2ubuntu10.9
libcurl4t64 8.5.0-2ubuntu10.9

Ubuntu 22.04 LTS
curl 7.81.0-1ubuntu1.24
libcurl3-gnutls 7.81.0-1ubuntu1.24
libcurl3-nss 7.81.0-1ubuntu1.24
libcurl4 7.81.0-1ubuntu1.24

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

References:
https://ubuntu.com/security/notices/USN-8227-1
CVE-2026-4873, CVE-2026-5545, CVE-2026-5773, CVE-2026-6253,
CVE-2026-6276, CVE-2026-6429, CVE-2026-7168

Package Information:
https://launchpad.net/ubuntu/+source/curl/8.18.0-1ubuntu2.1
https://launchpad.net/ubuntu/+source/curl/8.14.1-2ubuntu1.3
https://launchpad.net/ubuntu/+source/curl/8.5.0-2ubuntu10.9
https://launchpad.net/ubuntu/+source/curl/7.81.0-1ubuntu1.24

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