CVE-2019-1547

What it actually does

Allows full recovery of EC private keys via side-channel attack on ECDSA signatures when using explicit curve parameters without cofactor, bypassing side-channel protections in libcrypto.

Why it matters to the business

Attackers may obtain private keys used for signing or encryption, leading to potential compromise of secure communications, data integrity, and authentication across systems relying on affected OpenSSL versions.

How an attack unfolds

An attacker with local access identifies an application performing ECDSA signatures with explicit parameters lacking a cofactor, then times a large number of such operations to recover the private key through analysis of non-side-channel-resistant code paths.

How to fix it

Upgrade to OpenSSL 1.1.1d, 1.1.0l, or 1.0.2t (or later releases in each branch). Avoid constructing EC groups with explicit parameters; prefer named curves.

How to confirm the fix worked

Confirm installed OpenSSL version meets or exceeds 1.1.1d, 1.1.0l, or 1.0.2t. Audit source code and configurations for any use of explicit EC parameters with d2i_ECParameters or similar functions.

Typical attack path

1. Locate applications or libraries using explicit EC parameters instead of named curves
2. Trigger or observe a high volume of ECDSA signature operations
3. Collect precise timing data across many signatures
4. Apply mathematical recovery techniques such as lattice attacks to extract the private key

How to detect it

Post-exploitation detection is challenging because the attack relies on passive timing of normal operations; review logs for unusually high volumes of ECDSA operations using custom curves and inspect any available application-level timing or debug output.

What your security team should do

• Prioritize upgrade of all OpenSSL installations to a fixed release
• Scan codebases and configurations for explicit EC parameter usage
• Replace any custom curves with standard named curves where possible
• Review cryptographic key material that may have been exposed on affected systems