CVE-2023-26432 in OX App Suite
Summary
by MITRE • 06/20/2023
When adding an external mail account, processing of SMTP "capabilities" responses are not limited to plausible sizes. Attacker with access to a rogue SMTP service could trigger requests that lead to excessive resource usage and eventually service unavailability. We now limit accepted SMTP server response to reasonable length/size. No publicly available exploits are known.
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Analysis
by VulDB Data Team • 07/15/2023
This vulnerability resides in the handling of SMTP capabilities responses during external mail account configuration processes. The flaw represents a classic resource exhaustion issue where the system fails to impose reasonable limits on the size and length of responses received from SMTP servers. When users attempt to add external mail accounts, the system processes SMTP server capabilities responses without adequate size restrictions, creating an opportunity for malicious actors to exploit this weakness through specially crafted responses from rogue SMTP services.
The technical implementation of this vulnerability stems from inadequate input validation and resource management within the mail account provisioning workflow. The system processes SMTP capabilities responses without enforcing maximum length constraints or memory allocation limits, allowing attackers to send oversized responses that consume excessive system resources. This type of vulnerability aligns with CWE-770, which addresses allocation of resources without proper limits, and represents a form of resource exhaustion attack that can lead to denial of service conditions. The attack vector specifically targets the SMTP protocol negotiation phase where servers communicate their supported capabilities to client systems.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the overall availability and stability of mail services. When exploited, the vulnerability can cause memory exhaustion, CPU overutilization, and system resource starvation that affects not only the targeted mail server but potentially impacts other services running on the same infrastructure. This vulnerability can be particularly dangerous in environments where mail services are critical for business operations, as it could lead to complete service unavailability. The threat model aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and specifically targets the availability aspect of the CIA triad.
The mitigation strategy implemented by the affected systems involves enforcing reasonable limits on SMTP server response sizes, effectively preventing the exploitation of this vulnerability through oversized response handling. This solution addresses the root cause by establishing clear boundaries on resource allocation during SMTP capability processing, preventing attackers from consuming excessive system resources through crafted responses. The fix demonstrates proper defensive programming practices by implementing input validation and resource limitation mechanisms that align with secure coding guidelines. Organizations should ensure that all SMTP communication components implement similar size limits and validation checks to prevent similar vulnerabilities from manifesting in their environments. The solution represents a fundamental security improvement that aligns with industry best practices for preventing resource exhaustion attacks and maintaining system availability.