CVE-2021-22890: Medium severity libcurl vulnerability
A flaw was found in the way libcurl handled TLS 1.3 session tickets. A malicious HTTPS proxy could possibly use this flaw to make libcurl resume a TLS session it previously had with the proxy while intending to resume a TLS session with a target server, making it possible for the proxy to perform a man-in-the-middle attack.
Other sources
curl 7.63.0 to and including 7.75.0 includes vulnerability that allows a malicious HTTPS proxy to MITM a connection due to bad handling of TLS 1.3 session tickets. When using a HTTPS proxy and TLS 1.3, libcurl can confuse session tickets arriving from the HTTPS proxy but work as if they arrived from the remote server and then wrongly "short-cut" the host handshake. When confusing the tickets, a HTTPS proxy can trick libcurl to use the wrong session ticket resume for the host and thereby circumvent the server TLS certificate check and make a MITM attack to be possible to perform unnoticed. Note that such a malicious HTTPS proxy needs to provide a certificate that curl will accept for the MITMed server for an attack to work - unless curl has been told to ignore the server certificate check.
When confusing the tickets, a HTTPS proxy can trick libcurl to use the wrong session ticket resume for the host and thereby circumvent the server TLS certificate check and make a MITM attack to be possible to perform unnoticed.
Upstream Advisory:
https://curl.se/docs/CVE-2021-22890.html
— Red Hat
Affected Software
Remediation
Patch Available
Patch Available
Event History
Parent advisories
This vulnerability appears in the following advisories.
Frequently Asked Questions
What is CVE-2021-22890?
CVE-2021-22890 is a vulnerability in libcurl that allows a malicious HTTPS proxy to perform a Man-in-the-Middle attack on a connection.
Which versions of curl are affected by CVE-2021-22890?
curl versions 7.63.0 to 7.75.0 are affected by CVE-2021-22890.
How can a malicious HTTPS proxy exploit CVE-2021-22890?
A malicious HTTPS proxy can exploit CVE-2021-22890 by confusing session tickets and performing a Man-in-the-Middle attack on TLS 1.3 connections.
What is the severity of CVE-2021-22890?
CVE-2021-22890 has a severity value of 3.7, which is considered low.
Where can I find more information about CVE-2021-22890?
You can find more information about CVE-2021-22890 on the CVE website, NIST NVD, and the official curl documentation.