CVE-2020-36477

Name: CVE-2020-36477
Creator: NVD / NIST
Published: 2021-08-23T02:15:07.043+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 5.9/10EPSS 0.77%

Last modified Jun 17, 2026

CVE-2020-36477 is a medium-severity vulnerability rated 5.9/10 on the CVSS scale. 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. EPSS estimates a 0.77% chance of exploitation in the next 30 days.

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).

Metrics

CVSS 3.1

5.9/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS Probability

0.77%

51.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-295

Affected Software

Vendor	Product	Versions
Arm	Mbed Tls	< 2.24.0

References

https://github.com/ARMmbed/mbedtls/issues/3498Third Party Advisory
https://github.com/ARMmbed/mbedtls/releases/tag/v2.24.0Release Notes, Third Party Advisory
https://security.gentoo.org/glsa/202301-08Third Party Advisory
https://github.com/ARMmbed/mbedtls/issues/3498Third Party Advisory
https://github.com/ARMmbed/mbedtls/releases/tag/v2.24.0Release Notes, Third Party Advisory
https://security.gentoo.org/glsa/202301-08Third Party Advisory

Timeline

Published: Aug 23, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2020-36477?

How severe is CVE-2020-36477?

CVE-2020-36477 has a CVSS score of 5.9/10 (MEDIUM severity). The EPSS model estimates a 0.77% probability of exploitation in the next 30 days.

How do I fix CVE-2020-36477?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2020-36477?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST