CVE-2020-36478

Name: CVE-2020-36478
Creator: NVD / NIST
Published: 2021-08-23T02:15:07.097+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.5/10EPSS 1.13%

Last modified Jun 17, 2026

CVE-2020-36478 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. An issue was discovered in Mbed TLS before 2.25.0 (and before 2.16.9 LTS and before 2.7.18 LTS). A NULL algorithm parameters entry looks identical to an array of REAL (size zero) and thus the certificate is considered valid. EPSS estimates a 1.13% chance of exploitation in the next 30 days.

Description

An issue was discovered in Mbed TLS before 2.25.0 (and before 2.16.9 LTS and before 2.7.18 LTS). A NULL algorithm parameters entry looks identical to an array of REAL (size zero) and thus the certificate is considered valid. However, if the parameters do not match in any way, then the certificate should be considered invalid.

Metrics

CVSS 3.1

7.5/10

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

EPSS Probability

1.13%

62.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-295

Affected Software

Vendor	Product	Versions
Arm	Mbed Tls	< 2.7.18
Arm	Mbed Tls	>= 2.8.0, < 2.16.9
Arm	Mbed Tls	>= 2.17.0, < 2.25.0
Siemens	Logo\! Cmr2020 Firmware	< 2.2
Siemens	Logo\! Cmr2040 Firmware	< 2.2
Siemens	Simatic Rtu3031c Firmware	All versions
Siemens	Simatic Rtu3041c Firmware	All versions
Siemens	Simatic Rtu3030c Firmware	All versions
Siemens	Simatic Rtu3000c Firmware	All versions
Debian	Debian Linux	9.0
Debian	Debian Linux	10.0

References

https://cert-portal.siemens.com/productcert/pdf/ssa-756638.pdfPatch, Third Party Advisory
https://github.com/ARMmbed/mbedtls/issues/3629Exploit, Third Party Advisory
https://github.com/ARMmbed/mbedtls/releases/tag/v2.16.9Release Notes, Third Party Advisory
https://github.com/ARMmbed/mbedtls/releases/tag/v2.25.0Release Notes, Third Party Advisory
https://github.com/ARMmbed/mbedtls/releases/tag/v2.7.18Release Notes, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/11/msg00021.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/12/msg00036.htmlMailing List, Third Party Advisory
https://cert-portal.siemens.com/productcert/pdf/ssa-756638.pdfPatch, Third Party Advisory
https://github.com/ARMmbed/mbedtls/issues/3629Exploit, Third Party Advisory
https://github.com/ARMmbed/mbedtls/releases/tag/v2.16.9Release Notes, Third Party Advisory
https://github.com/ARMmbed/mbedtls/releases/tag/v2.25.0Release Notes, Third Party Advisory
https://github.com/ARMmbed/mbedtls/releases/tag/v2.7.18Release Notes, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2021/11/msg00021.htmlMailing List, Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/12/msg00036.htmlMailing List, Third Party Advisory

Timeline

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

Frequently Asked Questions

What is CVE-2020-36478?

How severe is CVE-2020-36478?

CVE-2020-36478 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 1.13% probability of exploitation in the next 30 days.

How do I fix CVE-2020-36478?

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-2020-36478?

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

Scan your code now

Source: NVD / NIST