CVE-2021-28363 Using default SSLContext for HTTPS requests in an HTTPS proxy doesn't verify certificate hostname for proxy connection

What is CVE-2021-28363?

CVE-2021-28363 is a medium-severity vulnerability in Fedoraproject Fedora, published on 15 Mar 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-295

Which versions are affected by CVE-2021-28363?

3 open source packages ship an affected version, including urllib3. It affects 3 products.

Products include Fedoraproject Fedora, Oracle Peoplesoft Enterprise Peopletools, Python Urllib3.

How do I fix CVE-2021-28363?

Upgrade urllib3 to 1.26.4 or later.

Is CVE-2021-28363 being exploited?

There is no known exploitation of CVE-2021-28363 in the wild and no public exploit code.

Other vulnerabilities in Fedoraproject Fedora

• CVE-2024-4577 PHP-CGI OS Command Injection Exploited Critical 9.8
• CVE-2021-39226 Grafana Authentication Bypass Exploited Critical 9.8
• CVE-2019-5544 VMware ESXi and Horizon DaaS OpenSLP Heap-Based Buffer Overflow Exploited Critical 9.8
• CVE-2024-4947 Google Chromium V8 Type Confusion Exploited Critical 9.6
• CVE-2024-4671 Google Chromium Visuals Use-After-Free Exploited Critical 9.6

All Fedoraproject Fedora vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as ALPINE-CVE-2021-28363, CLEANSTART-2026-AK39245, CLEANSTART-2026-MO57102, DEBIAN-CVE-2021-28363, GHSA-5phf-pp7p-vc2r, PYSEC-2021-59 and 2 more.