Summary

A leading market player faced significant costs and operational risk due to the presence of the Sweet32 vulnerability (CVE-2016-2183) on its critical business servers. Qyntar performed a practical exploit assessment combining laboratory testing, traffic analysis, and controlled attack attempts. The study demonstrated that the vulnerability was not exploitable in the client’s environment, allowing decision-makers to defer a costly migration and save tens of millions of forints while avoiding disruption of business-critical systems.

Background

Reports indicated that the company’s servers were affected by the high-severity Sweet32 vulnerability (CVE-2016-2183), which arises from the block size limitations of the TLS 3DES algorithm and can allow decryption of encrypted communication. As a consequence, there could be unauthorized access to customer data, account takeover, transaction manipulation, and severe compliance as well as reputational risks.

External recommendations suggested upgrading and partially replacing the affected servers’ operating systems, since the legacy operating system did not allow the vulnerability to be addressed with a simple configuration change. This, however, would have entailed significant costs. Such a migration would have been highly disruptive, requiring not only OS replacement but also changes to applications, middleware, and dependencies. The effort was expected to involve substantial development and operations hours, significant licensing fees, extensive regression testing, and unavoidable downtime affecting business-critical services.

The company therefore asked Qyntar to objectively examine whether the Sweet32 vulnerability could actually be exploited in their specific environment.

Methodology – Exploit assessment

During the assessment, we tested the practical exploitability of the vulnerability not only on a theoretical basis but also through controlled attack attempts. As a first step, we created clients that were able to force the server to use the 3DES cipher, ensuring that the conditions required for a Sweet32 attack were theoretically met.

1. Laboratory tests
   In the first phase, we reproduced the conditions of the Sweet32 attack in a laboratory environment. We built a test system equivalent to the client’s servers, enabled 3DES in the TLS configuration, and attempted to extract data from the encrypted channel. The experiments confirmed that if a sufficient amount of data accumulates within a single session, the vulnerability can in fact be exploited and the integrity of encryption compromised. This demonstrated that the threat is theoretically real.
2. Traffic analysis at the client
   Next, we extended the assessment to the client’s production environment and carried out detailed traffic analysis on the servers hosting critical web applications. The TLS session analysis revealed that connection durations were typically short, keys were regularly renegotiated, and no connection ever generated more than a few gigabytes of traffic. This volume fell far short of the tens of gigabytes required for Sweet32’s statistical collisions to occur.
3. Real attack attempts
   In the third phase, under controlled conditions and with the client’s awareness of potential risks, we carried out real attack attempts against the client’s production web applications. During testing, we succeeded in negotiating the use of the 3DES cipher. After establishing the connections, we attempted to generate targeted traffic within a single TLS session to approach the tens of gigabytes required for statistical collisions and compromise of the encryption.
   In practice, however, the attempts consistently failed. In the examined environment, TLS sessions were terminated early, key renegotiations occurred frequently, and no single connection remained open long enough to accumulate the necessary data. The short lifetime of the sessions and the volume of traffic on their own prevented the completion of the attack chain.
   We therefore concluded that neither the required continuity of data flow nor the necessary concentration of data was achieved within a single connection. All exploit attempts failed before reaching the traffic threshold demanded by Sweet32.

Results and Business Impact

Although Sweet32 was formally present on the servers, in the assessed environment its practical exploitation was determined to be unrealistic. Both theoretical analysis and controlled attack attempts demonstrated that traffic patterns, session lifetimes, and network topology prevented the conditions required for a successful attack.

Based on documented evidence from laboratory reproductions and on-site tests, decision-makers were able to confidently postpone a costly migration project. This avoided expenses estimated in the tens of millions of forints, including licensing, development, retesting, operational hours, and downtime-related business losses, and ensured that technical staff remained focused on strategic business initiatives instead of system reinstallation.

As a result, the client not only saved money but also avoided the risky reinstallation of business-critical systems and the associated service downtime.

Conclusion

This case demonstrates the value of a technical exploit assessment, supported by real-world attack attempts, in distinguishing theoretical vulnerabilities from actual threats.In this way, organizations can avoid unnecessary costs while directing their resources toward solving genuinely critical security issues.

(Note on disclosure
Due to the sensitive nature of the subject matter, certain technical details have intentionally been omitted from this case study. )