CVE-2018-20997

Vulnerability

Overview

The openssl crate for Rust, which provides bindings to OpenSSL, contained a use-after-free vulnerability in its CMS (Cryptographic Message Syntax) signing functionality. The root cause was improper memory management: a reference to freed memory was used after deallocation during CMS signing operations [1][3].

Exploitation

This vulnerability can be triggered remotely without authentication or user interaction. The CVSS vector (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) indicates a network attack vector with low complexity, no privileges required, and no user interaction needed [2][3]. An attacker could craft a malicious CMS message that, when processed by an application using the vulnerable crate, triggers the use-after-free.

Impact

Successful exploitation could lead to memory corruption, potentially allowing arbitrary code execution, denial of service, or information disclosure. The CVSS score of 9.8 (Critical) reflects the high impact on confidentiality, integrity, and availability [2][3].

Mitigation

The issue was patched in openssl crate version 0.10.9. Users should update to at least this version. The RustSec advisory (RUSTSEC-2018-0010) provides full details and references the fix [1][3].