CVE-2020-36477 Security feature bypass in n/a
Attackers can bypass X.509 certificate validation by exploiting improper SubjectAltName type checking, allowing impersonation of domains via IP address certificates.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2020-36477?
CVE-2020-36477 is a medium-severity vulnerability in Arm Mbed Tls, published on 23 Aug 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
An issue was discovered in Mbed TLS before 2.24.0. The verification of X.509 certificates when matching the expected common name (the cn argument of mbedtls_x509_crt_verify) with the actual certificate name is mishandled: when the subjecAltName extension is present, the expected name is compared to any name in that extension regardless of its type. This means that an attacker could impersonate a 4-byte or 16-byte domain by getting a certificate for the corresponding IPv4 or IPv6 address (this would require the attacker to control that IP address, though).
Weakness: CWE-295
Which versions are affected by CVE-2020-36477?
It affects 1 product.
Products include Arm Mbed Tls.
How do I fix CVE-2020-36477?
Upgrade to a fixed version.
Is CVE-2020-36477 being exploited?
There is no known exploitation of CVE-2020-36477 in the wild and no public exploit code.
Other vulnerabilities in Arm Mbed Tls
Sources
Also known as DEBIAN-CVE-2020-36477, GHSA-qfcq-wvh3-6p75, JLSEC-2025-212, UBUNTU-CVE-2020-36477.