CVE-2025-32433 impacts Erlang/OTP

The CVE-2025-32433 vulnerability, identified in the Erlang/OTP SSH library, is a severe remote code execution (RCE) flaw that allows unauthenticated attackers to execute arbitrary commands during SSH protocol negotiations. With the release of a proof-of-concept (PoC) exploit, this vulnerability has become a high-priority threat for systems using the Erlang/OTP platform, which powers critical applications in telecommunications, databases, and other enterprise solutions.

This in-depth analysis outlines the vulnerability’s technical details, its impact, the exploit mechanism, and comprehensive mitigation strategies to protect affected systems.

1. Overview of CVE-2025-32433

CVE-2025-32433 is a logical flaw in the SSH module of the Erlang/OTP runtime environment, specifically in its handling of SSH protocol messages. Attackers can exploit this flaw by sending malformed or unexpected messages during the SSH handshake, bypassing authentication and gaining control over vulnerable systems.

• Vulnerability Type: Remote Code Execution (RCE).
• Severity Level: Critical (CVSS Score: 10.0).
• Affected Component: Erlang/OTP SSH library.
• Exploitation Complexity: Low – No authentication or user interaction required.

2. Affected Versions

The vulnerability exists in multiple versions of Erlang/OTP prior to the following patched versions:

• OTP 27.3.3
• OTP 26.2.5.11
• OTP 25.3.2.20

Organizations using any version older than these releases are at risk and must urgently update their systems to eliminate exposure.

3. Exploit Mechanism

The exploit chain relies on leveraging the improper handling of SSH protocol negotiation messages in Erlang/OTP’s SSH implementation.

Step 1: Malformed SSH Messages

• The attacker initiates an SSH connection to the vulnerable server and sends crafted SSH protocol messages during the negotiation phase.
• These messages violate standard SSH protocol sequences but are processed incorrectly by the vulnerable SSH server.

Step 2: Arbitrary Command Execution

• The vulnerable server processes the unexpected messages and executes malicious code embedded within the crafted messages.
• This execution occurs before user authentication is completed, bypassing all access controls.

Step 3: Full System Compromise

• Once the attacker gains execution capabilities, they can:
• Execute arbitrary system commands.
• Install additional malware or backdoors.
• Escalate privileges to root-level access if the SSH service runs with elevated privileges.

Public PoC Exploit

The proof-of-concept (PoC) exploit, now publicly available, significantly increases the risk of mass exploitation, enabling attackers to rapidly weaponize the vulnerability. The PoC demonstrates the ease of exploitation and provides a framework for attackers to automate attacks.

4. Security Impact

A. System-Level Compromise

The flaw allows attackers to gain unauthenticated remote access, potentially compromising the entire system. If the SSH service runs with elevated privileges, attackers can achieve complete system control.

B. Potential for Widespread Attacks

The availability of the PoC exploit means attackers can target unpatched systems across the internet at scale. Systems running Erlang/OTP in production environments, such as telecommunications infrastructure, IoT devices, and databases, are particularly vulnerable.

C. Supply Chain Risks

Erlang/OTP is commonly embedded in third-party applications, meaning that organizations may be unaware of the vulnerable component’s presence in their software stack, increasing risks.

5. Mitigation Strategies

Organizations must act immediately to reduce their exposure to CVE-2025-32433. Below are comprehensive mitigation steps:

A. Apply Security Patches

• Upgrade to the latest patched versions of Erlang/OTP:
• OTP 27.3.3
• OTP 26.2.5.11
• OTP 25.3.2.20
• These updates address the improper SSH protocol message handling and effectively block exploitation attempts.

B. Restrict SSH Access

• Use firewall rules to allow SSH access only from trusted IP addresses.
• Disable public SSH exposure for Erlang/OTP instances unless absolutely necessary.

C. Temporary Workarounds

If immediate patching is not feasible, consider the following:

• Disable the Erlang/OTP SSH service temporarily.
• Monitor SSH connection attempts using intrusion detection systems (IDS) to identify malicious activity.

D. Monitor for Exploitation Indicators

• Regularly audit system logs for signs of unusual SSH activity, such as unexpected connection attempts or protocol errors.
• Implement endpoint detection and response (EDR) solutions to flag arbitrary command execution.

6. Conclusion

CVE-2025-32433 poses a severe risk to organizations leveraging Erlang/OTP, particularly in mission-critical applications. The release of a public PoC exploit emphasizes the urgency of patching systems and implementing immediate mitigations.

By addressing this vulnerability through upgrades, monitoring, and access control measures, organizations can significantly reduce the likelihood of exploitation. Given the broad use of Erlang/OTP in enterprise environments, comprehensive auditing of software dependencies is also critical to identifying hidden vulnerabilities in embedded libraries.