CVE-2021-28363
MEDIUMEPSS 80th pctlDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Exploit Intelligence
Elevated risk: more likely to be exploited than 80% of all known CVEs.
References
Related Vulnerabilities
Other CWE-295 (Improper Certificate Validation) vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2015-4000 | Low | 3.7 | 100% | - | Fix |
| CVE-2020-0601 | High | 8.1 | 89% | KEV | Fix |
| CVE-2009-3555 | Critical | 9.8 | 87% | - | Fix |
| CVE-2022-26923 | High | 8.8 | 83% | KEV | Fix |
| CVE-2023-27823 | Critical | 9.8 | 53% | - | - |
| CVE-2022-42979 | High | 8.8 | 24% | - | - |
Common questions
How do I fix CVE-2021-28363?
Upgrade python-urllib3 on debian 11 to 1.26.4-1 or later.
Is CVE-2021-28363 being actively exploited?
Not that we know of. CVE-2021-28363 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 2.1% is the estimated probability that it will be exploited in the next 30 days. That is higher than 80% of all scored CVEs.
How severe is CVE-2021-28363?
CVE-2021-28363 has a CVSS v3 base score of 6.5, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-28363 affect?
Published advisories record a fix for python-urllib3 (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.