CVE-2020-10932: arm mbed_tls Observable Discrepancy

Vulnerability summary

CVE-2020-10932 is a medium (CVSS 4.7) Observable Discrepancy vulnerability in arm mbed_tls. EPSS estimates a 0.25% chance of exploitation in the next 30 days, higher than 15.2% of scored vulnerabilities.

Timeline

1. 15-04-2020
   PublishedVulnerability first disclosed.
2. 04-08-2024
   Last modifiedVulnerability information updated.

Description

An issue was discovered in Arm Mbed TLS before 2.16.6 and 2.7.x before 2.7.15. An attacker that can get precise enough side-channel measurements can recover the long-term ECDSA private key by (1) reconstructing the projective coordinate of the result of scalar multiplication by exploiting side channels in the conversion to affine coordinates; (2) using an attack described by Naccache, Smart, and Stern in 2003 to recover a few bits of the ephemeral scalar from those projective coordinates via several measurements; and (3) using a lattice attack to get from there to the long-term ECDSA private key used for the signatures. Typically an attacker would have sufficient access when attacking an SGX enclave and controlling the untrusted OS.

• CWE-203Observable DiscrepancyThe product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.
• CWE-327Use of a Broken or Risky Cryptographic AlgorithmThe product uses a broken or risky cryptographic algorithm or protocol.