A significant security flaw has been identified in the Erlang/Open Telecom Platform (OTP) SSH implementation, potentially allowing attackers to execute arbitrary code without authentication under specific conditions. This vulnerability, designated as CVE-2025-32433, has been assigned the highest possible CVSS score of 10.0, indicating its critical severity.
Understanding the Vulnerability
The core of this issue lies in the improper handling of SSH protocol messages within the Erlang/OTP SSH library. Specifically, the system fails to adequately verify the size of SFTP packets. Consequently, when multiple SSH packets—each adhering to the maximum SSH packet size—are received, they can be combined into a single SFTP packet that exceeds the allowed size. This scenario can lead to excessive memory allocation, potentially resulting in a denial-of-service (DoS) condition. Notably, this vulnerability can only be exploited by authenticated users who have completed the SSH handshake process.
Potential Impact
If exploited, this vulnerability could allow an attacker to execute arbitrary code within the context of the SSH daemon. The severity escalates if the daemon operates with root privileges, granting the attacker full control over the affected device. This control could lead to unauthorized access, data manipulation, or service disruption. Given Erlang’s widespread use in high-availability systems, including those from major vendors like Cisco and Ericsson, the potential impact is substantial.
Affected Versions and Patches
The vulnerability affects all users running an SSH server based on the Erlang/OTP SSH library. To address this issue, patches have been released in the following versions:
– OTP-27.2.4
– OTP-26.2.5.9
– OTP-25.3.2.18
Users are strongly encouraged to update to these patched versions promptly to mitigate the risk associated with this vulnerability.
Mitigation Strategies
In addition to applying the necessary patches, organizations can implement temporary workarounds to reduce exposure. One effective measure is to restrict access to vulnerable SSH servers using appropriate firewall rules, thereby limiting potential attack vectors. However, these workarounds should not be considered permanent solutions, and updating to the patched versions remains the recommended course of action.
Broader Context
This vulnerability underscores the critical importance of rigorous input validation and protocol handling in software development, especially for systems designed to be highly available and secure. It also highlights the necessity for organizations to stay vigilant and proactive in applying security updates to protect against emerging threats.
Conclusion
The discovery of CVE-2025-32433 serves as a stark reminder of the ever-present risks in network security. Organizations utilizing the Erlang/OTP SSH library must take immediate action to apply the available patches and review their security measures to prevent potential exploitation. Staying informed and responsive to such vulnerabilities is essential in maintaining the integrity and security of critical systems.
