What’s Vulnerable › Vulnerabilities

CVE-2020-36475

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-08-23 · updated 2026-06-17
• Weakness: CWE-131

Description

An issue was discovered in Mbed TLS before 2.25.0 (and before 2.16.9 LTS and before 2.7.18 LTS). The calculations performed by mbedtls_mpi_exp_mod are not limited; thus, supplying overly large parameters could lead to denial of service when generating Diffie-Hellman key pairs.

Affected products

• mbedtls: before 2.7.18; from 2.8.0 before 2.16.9; from 2.17.0 before 2.25.0 — fixed in 2.16.9, 2.25.0, 2.7.18
• Debian Linux: 9.0, 10.0
• Siemens Logo! Cmr2020 Firmware: before 2.2 — fixed in 2.2
• Siemens Logo! Cmr2040 Firmware: before 2.2 — fixed in 2.2
• Siemens Simatic Rtu3000C Firmware: all versions
• Siemens Simatic Rtu3030C Firmware: all versions
• Siemens Simatic Rtu3031C Firmware: all versions
• Siemens Simatic Rtu3041C Firmware: all versions

How to fix

Upgrade to a fixed version: mbedtls 2.16.9, 2.25.0, 2.7.18; Siemens Logo! Cmr2020 Firmware 2.2; Siemens Logo! Cmr2040 Firmware 2.2. Check the vendor advisory for mitigations.

References

• https://cert-portal.siemens.com/productcert/pdf/ssa-756638.pdf
• https://github.com/ARMmbed/mbedtls/releases/tag/v2.16.9
• https://github.com/ARMmbed/mbedtls/releases/tag/v2.25.0
• https://github.com/ARMmbed/mbedtls/releases/tag/v2.7.18
• https://lists.debian.org/debian-lts-announce/2021/11/msg00021.html
• https://lists.debian.org/debian-lts-announce/2022/12/msg00036.html
• https://cert-portal.siemens.com/productcert/pdf/ssa-756638.pdf
• https://github.com/ARMmbed/mbedtls/releases/tag/v2.16.9
• https://github.com/ARMmbed/mbedtls/releases/tag/v2.25.0
• https://github.com/ARMmbed/mbedtls/releases/tag/v2.7.18
• https://lists.debian.org/debian-lts-announce/2021/11/msg00021.html
• https://lists.debian.org/debian-lts-announce/2022/12/msg00036.html

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