CVE-2024-23573: HCL Aftermarket EPC Lucky 13 Vulnerability

CVE-2024-23573 Overview

CVE-2024-23573 affects HCL Aftermarket EPC because the application implements TLS in a way that is vulnerable to the Lucky 13 attack. Lucky 13 is a timing side-channel weakness in the CBC-mode MAC-then-encrypt construction used by TLS. An attacker positioned on the network can measure small timing differences during message authentication to recover portions of encrypted plaintext. The flaw affects TLS 1.1, TLS 1.2, and DTLS 1.0 or 1.2 implementations, and also legacy SSL 3.0 and TLS 1.0. Exploitation typically requires a man-in-the-middle position and a large number of captured or induced ciphertexts.

Critical Impact
A network-adjacent attacker can recover small portions of plaintext transmitted through the affected TLS sessions using a timing side channel.

Affected Products

HCL Aftermarket EPC
TLS 1.1, TLS 1.2, DTLS 1.0, and DTLS 1.2 implementations within the affected application
Legacy SSL 3.0 and TLS 1.0 configurations

Discovery Timeline

2026-07-17 - CVE-2024-23573 published to NVD
2026-07-17 - Last updated in NVD database

Technical Details for CVE-2024-23573

Vulnerability Analysis

The issue is classified under [CWE-425] Forceable Execution of Code Path, but the underlying weakness is a cryptographic timing side channel. In CBC-based TLS cipher suites, the record layer decrypts a ciphertext, removes PKCS#7 padding, and then verifies the HMAC. Because MAC verification and padding removal complete at slightly different times when the padding is malformed, an attacker can distinguish between valid and invalid padding by measuring server response latency.

With sufficient captured traffic and induced retransmissions, the attacker recovers small blocks of plaintext, most practically short repeated secrets such as session cookies or authentication tokens. Exploitation requires network positioning and a high volume of probe messages, which is why the attack complexity is rated high and the exploit is difficult in typical networks.

Root Cause

The root cause is continued support for CBC-mode cipher suites combined with the MAC-then-encrypt construction defined in TLS versions prior to 1.3. Any implementation that does not use constant-time MAC verification exposes measurable timing variance to network observers.

Attack Vector

An attacker must observe or intercept traffic between a client and the affected HCL Aftermarket EPC server. The attacker then induces or captures many TLS records containing the target secret at a fixed offset. By replaying modified ciphertext blocks and measuring timing differences in the server's error response, the attacker gradually recovers plaintext bytes. See the HCL Software Knowledge Base Article for vendor-specific technical details.

Detection Methods for CVE-2024-23573

Indicators of Compromise

Unusually high volumes of TLS handshake failures or MAC verification errors from a single client IP over short time windows.
Long-lived TLS sessions with repeated identical record lengths being replayed or retransmitted.
Presence of CBC-mode cipher suites negotiated between clients and the HCL Aftermarket EPC server.

Detection Strategies

Inventory TLS endpoints and flag any that negotiate TLS_RSA_WITH_AES_*_CBC_* or similar CBC-based suites on TLS 1.0, 1.1, or 1.2.
Monitor server logs for repeated bad_record_mac or padding-related alerts, which indicate active probing.
Use TLS scanning tools such as testssl.sh or sslyze against the application to confirm exposure to Lucky 13.

Monitoring Recommendations

Forward TLS handshake and alert telemetry to a centralized SIEM for correlation across sessions.
Alert on sustained man-in-the-middle indicators such as ARP anomalies, unexpected certificate changes, and repeated session resumption failures.
Track cipher suite usage over time to measure remediation progress after configuration changes.

How to Mitigate CVE-2024-23573

Immediate Actions Required

Apply the vendor guidance published in the HCL Software Knowledge Base Article.
Disable CBC-mode cipher suites on the HCL Aftermarket EPC server and prefer AEAD suites such as AES-GCM or ChaCha20-Poly1305.
Disable SSL 3.0, TLS 1.0, and TLS 1.1 on all listeners exposing the application.

Patch Information

HCL has published mitigation guidance in knowledge base article KB0132294. Administrators should follow the vendor's remediation steps and apply any updates referenced in that advisory. Where an in-product update is not yet available, administrators should enforce the configuration workarounds below and restrict network exposure of the affected service.

Workarounds

Enable TLS 1.2 with AEAD-only cipher suites, or upgrade to TLS 1.3, which removes CBC constructions entirely.
Terminate TLS at a hardened reverse proxy or load balancer configured to reject CBC cipher suites and legacy protocol versions.
Restrict network access to the HCL Aftermarket EPC service so that only trusted clients can reach the TLS listener, reducing opportunity for man-in-the-middle positioning.

bash

# Example: restrict cipher suites on an nginx TLS terminator fronting the application
ssl_protocols TLSv1.2 TLSv1.3;
ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305';
ssl_prefer_server_ciphers on;
ssl_session_tickets off;