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CVE-2021-22890

Published: 31 March 2021

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.

Notes

AuthorNote
alexmurray
affects curl versions between 7.63.0 and 7.75.0

Priority

Medium

Cvss 3 Severity Score

3.7

Score breakdown

Status

Package Release Status
curl
Launchpad, Ubuntu, Debian
bionic Not vulnerable
(code not present)
focal
Released (7.68.0-1ubuntu2.5)
groovy
Released (7.68.0-1ubuntu4.3)
trusty Not vulnerable
(code not present)
upstream Needs triage

xenial Not vulnerable
(code not present)
Patches:
vendor: https://curl.se/EQo2A9nBnMI68.patch

Severity score breakdown

Parameter Value
Base score 3.7
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact Low
Availability impact None
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N