Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Arm | Mbed Tls | < 2.16.11 |
Related Weaknesses (CWE)
References
- https://github.com/ARMmbed/mbedtls/releases/Third Party Advisory
- https://kouzili.com/Load-Step.pdfThird Party Advisory
- https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-Vendor Advisory
- https://github.com/ARMmbed/mbedtls/releases/Third Party Advisory
- https://kouzili.com/Load-Step.pdfThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2025/06/msg00034.html
- https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-Vendor Advisory
FAQ
What is CVE-2021-36647?
CVE-2021-36647 is a vulnerability with a CVSS score of 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 before 3.0.0, 2.27.0 or 2.16.11 allows attackers with access to pre...
How severe is CVE-2021-36647?
CVE-2021-36647 has been rated MEDIUM with a CVSS base score of 4.7/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2021-36647?
Check the references section above for vendor advisories and patch information. Affected products include: Arm Mbed Tls.