Side channel attack on ECDSA in Mbed TLS

1) Use of a broken or risky cryptographic algorithm

EUVDB-ID: #VU29653

Risk: Low

CVSSv3.1: 4.8 [CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2020-10932

CWE-ID: CWE-327 - Use of a Broken or Risky Cryptographic Algorithm

Exploit availability: No

Description

The vulnerability allows a local user to gain access to sensitive information.

The vulnerability exists due to incorrect implementation of modular inverse operation as implemented in Mbed TLS. An attacker 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) can fully recover an ECDSA private key after observing a number of signature operations a.k.k. single-trace side channel attack.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

mbed TLS: 2.0.0 - 2.21.0

External links

http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/FCWN5HIF4CJ2LZTOMEBJ7Q4IMMV7ZU2V/
http://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZNOS2IIBH5WNJXZUV546PY7666DE7Y3L/
http://tls.mbed.org/tech-updates/releases/mbedtls-2.16.6-and-2.7.15-released
http://tls.mbed.org/tech-updates/security-advisories
http://tls.mbed.org/tech-updates/security-advisories/mbedtls-security-advisory-2020-04

Q & A

Can this vulnerability be exploited remotely?

No. This vulnerability can be exploited locally. The attacker should have authentication credentials and successfully authenticate on the system.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.