Medium severity · published Jan 17, 2023
CVE-2021-36647
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…
4.7
CVSS
0.2%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N
Attack vector
Local
Complexity
High
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
None
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 6% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MT
Mbed Tls · Arm
before 2.16.11; 2.17.0 before 2.27.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-36647
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-36647
Third Party Advisory
https://github.com/ARMmbed/mbedtls/releases/
Third Party Advisory
https://kouzili.com/Load-Step.pdf
Vendor Advisory
https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1
lists.debian.org
https://lists.debian.org/debian-lts-announce/2025/06/msg00034.html
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