CVE-2021-36647

What it is

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.

At a glance

Exploitability

Can be exploited locally on the machine with a low-privilege account. High risk of data exposure.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2023-01-17 21:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-06-17 03:58 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 4.7 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2023-01-17 21:15 UTC

Last modified

2026-06-17 03:58 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-327 · Broken cryptographic algorithm

Record status

Modified

Affected

• Arm Mbed Tls < 2.16.11
• Arm Mbed Tls < 2.27.0
• Trustedfirmware Mbed Tls < 3.0.0

Attack profile CVSS 3.1 · 4.7

Attack vector

Local

Complexity

High

Privileges needed

Low

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-36647.md and follow it. Check whether this project is affected by CVE-2021-36647. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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