CVE-2021-36647

4.7 MEDIUM

Use of a Broken or Risky Cryptographic Algorithm in the function mbedtls_mpi_exp_mod() in lignum.c in Mbed TLS Mbed TLS all versions befo...

Published: 2023-01-17 · Last updated: 2026-06-05

Severity and scoring

CVSS: 4.7 MEDIUM
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
CWE: CWE-327

Affected products

Vendor	Product
arm	mbed_tls
trustedfirmware	mbed_tls

Description

Use of a Broken or Risky Cryptographic Algorithm in the function mbedtls_mpi_exp_mod() in lignum.c in Mbed TLS Mbed TLS all versions before 3.0.0, 2.27.0 or 2.16.11 allows attackers with access to precise enough timing and memory access information (typically an untrusted operating system attacking a secure enclave such as SGX or the TrustZone secure world) to recover the private keys used in RSA.

Source: NVD

References

[NVD]https://nvd.nist.gov/vuln/detail/CVE-2021-36647
[Other]https://github.com/ARMmbed/mbedtls/releases/
[Other]https://kouzili.com/Load-Step.pdf
[Vendor advisory]https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1
[Other]https://github.com/ARMmbed/mbedtls/releases/
[Other]https://kouzili.com/Load-Step.pdf
[Other]https://lists.debian.org/debian-lts-announce/2025/06/msg00034.html
[Vendor advisory]https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1

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