CVE-2024-13176: OpenSSL ECDSA Timing Side-Channel Leak

CVE-2024-13176 Overview

Issue summary: A timing side-channel which could potentially allow recovering the private key exists in the ECDSA signature computation.

Impact summary: A timing side-channel in ECDSA signature computations could allow recovering the private key by an attacker. However, measuring the timing would require either local access to the signing application or a very fast network connection with low latency.

Critical Impact

This vulnerability exploits a timing signal during ECDSA signature computations, potentially exposing private keys. While significant, the severity is reduced due to the need for proximity to the target system.

Affected Products

• OpenSSL 3.4, 3.3, 3.2, 3.1, 3.0

Discovery Timeline

• 2025-01-20 - CVE CVE-2024-13176 published to NVD
• 2025-11-03 - Last updated in NVD database

Technical Details for CVE-2024-13176

Vulnerability Analysis

A timing side-channel vulnerability has been identified in the ECDSA signature computation process. This vulnerability can be exploited by measuring subtle timing discrepancies that occur during signature operations, specifically when the top word of the inverted ECDSA nonce is zero. This leak is more probable with the NIST P-521 elliptic curve.

Root Cause

The issue arises due to the inconsistency in processing times during ECDSA signature generation, primarily associated with certain elliptic curves like NIST P-521 when dealing with zeroed nonce values.

Attack Vector

Physical proximity or a network environment with low latency is required to exploit this vulnerability. The attacker needs to measure minute variations in timing during the ECDSA operations.

// Example exploitation code (sanitized)
#include <openssl/ecdsa.h>

int main() {
    // Set up an environment to measure timing differences
    // specifically using the NIST P-521 curve
    // This code does not perform the attack but outlines an environment setup
    EC_KEY *key = EC_KEY_new_by_curve_name(NID_secp521r1);
    if (key == NULL) return 1;
    // Timing measurements would be inserted here
    // ...
    EC_KEY_free(key);
    return 0;
}

Detection Methods for CVE-2024-13176

Indicators of Compromise

• Unusual ECDSA operation logs
• High-frequency network traffic correlated with cryptographic operations
• Local access attempts with high privilege requirements

Detection Strategies

Monitor for access patterns or processes that anomalously increase ECDSA operation frequency, particularly on P-521 curves. Audit logs for irregular timing patterns associated with cryptographic operations should be analyzed.

Monitoring Recommendations

Implement advanced network and local monitoring using SentinelOne’s EDR capabilities to detect unusual timing-based attacks. Enable detailed logging for cryptographic operations on systems processing sensitive data.

How to Mitigate CVE-2024-13176

Immediate Actions Required

• Prioritize the deployment of patches provided by the OpenSSL project.
• Restrict network access to systems using vulnerable ECDSA implementations.
• Enhance system logging and monitoring to capture timing anomalies.

Patch Information

OpenSSL has released patches addressing this vulnerability. Users should update to the latest stable release (see OpenSSL advisory).

Workarounds

For environments where patching is not immediately feasible, consider disabling usage of the NIST P-521 curve in ECDSA operations.

# Configuration example
openssl.cnf:
[default_sect]
    no-nist-p521 = disable