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USN-5079-3: curl vulnerabilities

21 September 2021

USN-5079-1 introduced a regression in curl.



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


USN-5079-1 fixed vulnerabilities in curl. One of the fixes introduced a
regression on Ubuntu 18.04 LTS. This update fixes the problem.

We apologize for the inconvenience.

Original advisory details:

It was discovered that curl incorrect handled memory when sending data to
an MQTT server. A remote attacker could use this issue to cause curl to
crash, resulting in a denial of service, or possibly execute arbitrary
code. (CVE-2021-22945)

Patrick Monnerat discovered that curl incorrectly handled upgrades to TLS.
When receiving certain responses from servers, curl would continue without
TLS even when the option to require a successful upgrade to TLS was
specified. (CVE-2021-22946)

Patrick Monnerat discovered that curl incorrectly handled responses
received before STARTTLS. A remote attacker could possibly use this issue
to inject responses and intercept communications. (CVE-2021-22947)

Update instructions

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

Ubuntu 18.04

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