CVE-2021-36647

MEDIUM
4.7
CVSS Score
Published: January 17, 2023 at 12:00 AM UTC
Updated: June 17, 2026 at 03:58 AM UTC
2 products affected across 2 vendorsmbed TLSMbed TLS

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Severity
MEDIUM4.7
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 2.16.112.17.0 ≤ v < 2.27.0
Affected range stops below 2.16.11, so it looks safe — our inference, not a vendor statement
Affected range stops below 2.27.0, so it looks safe — our inference, not a vendor statement
2.28.0 ≤ v < 3.0.0
Affected range stops below 3.0.0, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

4.7MEDIUMCISA-ADP
Attack Vector
LOCAL
Complexity
HIGH
Privileges
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-327

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