CVE-2020-36478
HIGHCVSS 7.5/10EPSS 1.13%
Last modified
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/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Weakness Enumeration
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
- Last Modified
- Status
- Modified
Frequently Asked Questions
What is CVE-2020-36478?
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.
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.
How Strix Helps
- How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
- Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
- PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
- AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.
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Are you affected by CVE-2020-36478?
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