CVE-2025-26618 is a vulnerability classified under CWE-789 (Memory Allocation with Excessive Size Value) found in the Erlang OTP platform, specifically within its SSH server implementation handling SFTP packets. Erlang OTP is widely used for building scalable, high-availability systems, and its SSH server component processes incoming SSH packets, including those for SFTP operations. The vulnerability occurs because the system fails to properly validate the size of SFTP packets formed by concatenating multiple SSH packets, each conforming to the maximum SSH packet size. When these packets are combined, the resulting SFTP packet can exceed the maximum allowed size, leading the system to allocate an excessive amount of memory. This unchecked allocation can cause resource exhaustion, potentially resulting in denial of service (DoS) conditions. Exploitation requires an attacker to be a successfully authenticated user post-SSH handshake, meaning the attacker must have valid credentials or access tokens. No user interaction beyond authentication is necessary. The vulnerability affects OTP versions starting from 25.0 up to but not including 25.3.2.18, 26.0.0.0 up to 26.2.5.9, and 27.0.0 up to 27.2.4. The issue has been addressed in OTP versions 27.2.4, 26.2.5.9, and 25.3.2.18. No known exploits have been reported in the wild, and no workarounds exist, emphasizing the importance of applying official patches. The CVSS v4.0 score is 7.0 (high severity), reflecting network attack vector, high privileges required, and high impact on availability due to potential memory exhaustion. This vulnerability poses a significant risk to systems relying on Erlang OTP's SSH server for SFTP file transfers, especially in environments requiring high availability and robust security.

For European organizations, the impact of CVE-2025-26618 can be substantial, particularly for those utilizing Erlang OTP in critical infrastructure, telecommunications, financial services, or cloud platforms where Erlang is prevalent. The vulnerability can be exploited by authenticated users to cause excessive memory allocation, leading to denial of service and potential disruption of essential services. This can degrade system availability, impact business continuity, and increase operational costs due to downtime and recovery efforts. Organizations relying on SFTP over SSH for secure file transfers may face interruptions, affecting data exchange and automated workflows. Additionally, the requirement for authenticated access means insider threats or compromised credentials could be leveraged to exploit this vulnerability. The absence of workarounds and the need for patching underscore the urgency for affected entities to update their OTP versions promptly. Failure to do so could expose European organizations to service outages and potential reputational damage, especially in sectors with stringent uptime and security requirements.

1. Immediate patching: Upgrade Erlang OTP installations to versions 27.2.4, 26.2.5.9, or 25.3.2.18 or later, as these contain the fix for this vulnerability. 2. Access control: Restrict SSH access to trusted users only and enforce strong authentication mechanisms such as multi-factor authentication (MFA) to reduce the risk of unauthorized authenticated access. 3. Monitoring and alerting: Implement monitoring for unusual memory usage patterns or SSH session anomalies that could indicate exploitation attempts. 4. Network segmentation: Isolate critical systems running Erlang OTP SSH servers to limit exposure and lateral movement in case of compromise. 5. Credential management: Regularly audit and rotate SSH credentials and keys to minimize the risk of credential compromise. 6. Incident response readiness: Prepare response plans for potential denial of service incidents related to this vulnerability, including resource scaling and failover strategies. 7. Vendor communication: Stay informed through Erlang OTP vendor advisories and security bulletins for any updates or additional mitigations. These steps go beyond generic advice by focusing on controlling authenticated access, proactive monitoring, and operational readiness.