Security Bulletin: urllib upgrade CVE-2021-33503, CVE-2021-28363

Summary

The urllib3 library 1.26.x before 1.26.4 for Python omits SSL certificate validation in some cases involving HTTPS to HTTPS proxies. The initial connection to the HTTPS proxy (if an SSLContext isn’t given via proxy_config) doesn’t verify the hostname of the certificate. This means certificates for different servers that still validate properly with the default urllib3 SSLContext will be silently accepted.

Vulnerability Details

CVEID:CVE-2021-33503
**DESCRIPTION:**urllib3 is vulnerable to a denial of service, caused by a regular expression denial of service (ReDoS) flaw due to catastrophic backtracking. By sending a specially-crafted URL request, a remote attacker could exploit this vulnerability to cause a denial of service condition.
CVSS Base score: 5.3
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/203109 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L)

CVEID:CVE-2021-28363
**DESCRIPTION:**urllib3 for python is vulnerable to a man-in-the-middle attack, caused by improper certificate validation in some cases involving HTTPS to HTTPS proxies. An attacker could exploit this vulnerability to launch a man-in-the-middle attack and gain access to the communication channel between endpoints to obtain sensitive information or further compromise the system.
CVSS Base score: 5.9
CVSS Temporal Score: See: https://exchange.xforce.ibmcloud.com/vulnerabilities/198199 for the current score.
CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:L/A:N)

Affected Products and Versions

Remediation/Fixes

Upgraded to version 8.6.3 or 8.7.1

Workarounds and Mitigations

None