PT-2021-7637 · Arm+2 · Mbed Tls+2

Published 2021-07-07 · Updated 2025-06-30 · CVE-2021-36647

Positive Technologies (AI Summary)

CVSS v3.1

4.7

Medium

Base vector

AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N

Name of the Vulnerable Software and Affected Versions Mbed TLS versions prior to 3.0.0 Mbed TLS versions prior to 2.27.0 Mbed TLS versions prior to 2.16.11

Description The issue is related to the use of a broken or risky cryptographic algorithm in the mbedtls mpi exp mod() function in lignum.c in Mbed TLS. This allows attackers with access to precise enough timing and memory access information, typically an untrusted operating system attacking a secure enclave, to recover the private keys used in RSA.

Recommendations For versions prior to 3.0.0, update to version 3.0.0 or later. For versions prior to 2.27.0, update to version 2.27.0 or later. For versions prior to 2.16.11, update to version 2.16.11 or later. As a temporary workaround, consider restricting access to the mbedtls mpi exp mod() function in lignum.c until a patch is available.

Fix

Use of a Broken Cryptographic Algorithm

Weakness Enumeration

CWE-327

Related Identifiers

ALT-PU-2021-2163

ALT-PU-2021-2172

ALT-PU-2021-2234

AZL-13023

AZL-47713

BDU:2023-00604

CVE-2021-36647

DLA-4236-1

Affected Products

Alt Linux

Debian

Mbed Tls

References · 19

• https://osv.dev/vulnerability/AZL-13023 · Vendor Advisory
• https://osv.dev/vulnerability/DEBIAN-CVE-2021-36647 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2021-36647 · Vendor Advisory
• https://cve.org/CVERecord?id=CVE-2021-36647 · Security Note
• https://osv.dev/vulnerability/DLA-4236-1 · Vendor Advisory
• https://bdu.fstec.ru/vul/2023-00604 · Security Note
• https://nvd.nist.gov/vuln/detail/CVE-2021-36647 · Security Note
• https://ubuntu.com/security/CVE-2021-36647 · Vendor Advisory
• https://osv.dev/vulnerability/CVE-2021-36647 · Vendor Advisory
• https://osv.dev/vulnerability/AZL-47713 · Vendor Advisory
• https://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2021-07-1 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2021-36647 · Vendor Advisory
• https://github.com/Mbed-TLS/mbedtls/releases · Note
• https://github.com/ARMmbed/mbedtls/releases · Note
• https://t.me/cvenotify/118385 · Telegram Post