CVE-2021-36647

Summary

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.

Affected Software

Weaknesses

• n/a

ADP Enrichment

CVE Program Container

Additional References

• https://kouzili.com/Load-Step.pdf
• https://github.com/ARMmbed/mbedtls/releases/
• https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1
• https://lists.debian.org/debian-lts-announce/2025/06/msg00034.html

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: no
  • Technical Impact: partial

References

• https://kouzili.com/Load-Step.pdf
• https://github.com/ARMmbed/mbedtls/releases/
• https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1

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