USN-8487-2: curl regression

USN-8487-1 fixed vulnerabilities in curl. Unfortunately that update
contained an incomplete fix for CVE-2026-8927. This update fixes the
problem.

Original advisory details:

Andrew Nesbitt discovered that curl could reuse an existing live
connection during STARTTLS-based connection upgrades even when the TLS
configuration did not match. A remote attacker could possibly use this
issue to cause curl to use an unintended TLS configuration.
(CVE-2026-8286)

Muhamad Arga Reksapati discovered that curl incorrectly reused connections
for Negotiate-authenticated requests when different services were
involved. A remote attacker could possibly use this issue to access
resources authenticated for another service. This issue only affected
Ubuntu 18.04 LTS, Ubuntu 20.04 LTS, Ubuntu 22.04 LTS, Ubuntu 24.04 LTS,
Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-8458)

It was discovered that curl incorrectly handled cookie parsing in certain
circumstances. A remote attacker could possibly use this issue to set
cookies that would be transmitted to unrelated third-party domains. This
issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, Ubuntu 20.04 LTS,
Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu 26.04 LTS.
(CVE-2026-8924)

Joshua Rogers discovered that curl could double-free a GSASL context when
handling SASL authentication. A remote attacker could possibly use this
issue to cause a denial of service, or execute arbitrary code. This issue
only affected Ubuntu 22.04 LTS, Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu
26.04 LTS. (CVE-2026-8925)

Joshua Rogers discovered that curl could select the wrong password from a
.netrc file when a username was specified in the URL without a password. A
remote attacker could possibly use this issue to obtain sensitive
information. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS.
(CVE-2026-8926)

Ady Elouej discovered that curl did not clear proxy authentication state
between requests when reusing a handle with environment-variable proxy
configuration. A remote attacker could possibly use this issue to obtain
sensitive credentials. (CVE-2026-8927)

Guannan Wang, Zhanpeng Liu, Jiashuo Liang, and Guancheng Li discovered
that curl did not properly clear proxy authentication credentials when
instructed to do so. A remote attacker could possibly use this issue to
obtain sensitive credentials. This issue only affected Ubuntu 25.10 and
Ubuntu 26.04 LTS. (CVE-2026-9079)

Joshua Rogers discovered that curl contained a use-after-free when
curl_easy_pause() was called within the event-based socket callback. A
remote attacker could possibly use this issue to cause a denial of service
or possibly execute arbitrary code. This issue only affected Ubuntu 25.10
and Ubuntu 26.04 LTS. (CVE-2026-9080)

Eunsoo Kim discovered that curl could send early data on a resumed TLS
session before enforcing certificate verification failure. A machine-in-
the-middle attacker could possibly use this issue to obtain sensitive
information. This issue only affected Ubuntu 25.10 and Ubuntu 26.04 LTS.
(CVE-2026-9545)

Joshua Rogers discovered that curl did not properly reject host key type
mismatches when using the SSH key callback for SCP and SFTP transfers. A
machine-in-the-middle attacker could possibly use this issue to
impersonate a trusted server. This issue only affected Ubuntu 22.04 LTS,
Ubuntu 24.04 LTS, Ubuntu 25.10, and Ubuntu 26.04 LTS. (CVE-2026-9547)