CVE-2026-119762 in Mail Server
Summary
by MITRE • 10/30/2026
Axigen Mail Server before 10.5.69, 10.6.x before 10.6.40, and 10.7.x before 10.7.2 contains an unauthenticated denial of service vulnerability caused by unbounded nesting depth when parsing SOAP/XML and JSON request bodies before authentication. Attackers can send a single deeply nested request to WebMail, WebAdmin, or WebMail Proxy listeners to exhaust the stack and crash SMTP, IMAP, POP3, and web services repeatedly.
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Analysis
by VulDB Data Team • 10/30/2026
The vulnerability identified in Axigen Mail Server versions prior to 10.5.69, 10.6.x before 10.6.40, and 10.7.x before 10.7.2 represents a critical unauthenticated denial of service flaw rooted in improper input validation during the parsing of structured data formats. Specifically, the software fails to enforce limits on the nesting depth when processing SOAP/XML and JSON request bodies prior to completing user authentication. This architectural oversight allows external actors to exploit the parser's recursive nature by submitting payloads with excessively deep structural hierarchies. Because this check is bypassed before the authentication phase, any remote attacker can target these endpoints without needing valid credentials, significantly lowering the barrier for exploitation and increasing the attack surface across all exposed services including WebMail, WebAdmin, and the WebMail Proxy listeners.
From a technical perspective, the core issue lies in how the application handles recursive data structures within XML and JSON parsers. When a request body contains nested elements or objects that exceed an internal threshold without proper bounds checking, the underlying processing logic continues to allocate stack memory for each level of nesting. This unbounded recursion leads to rapid exhaustion of available system resources, specifically causing a stack overflow condition. The consequence is immediate instability within the affected services. Since Axigen Mail Server integrates multiple protocols such as SMTP, IMAP, and POP3 alongside its web-based interfaces, a crash in one component can have cascading effects or simply result in the complete unavailability of mail delivery and retrieval functions for all users connected to that instance.
The operational impact of this vulnerability is severe due to its potential for repeated exploitation. An attacker does not need to send multiple complex requests; a single carefully crafted, deeply nested payload is sufficient to trigger the crash. Furthermore, because the service components are often designed to restart or handle errors by attempting recovery, an automated attack script can repeatedly send these malicious payloads, leading to a persistent denial of service state. This effectively disrupts business continuity for organizations relying on Axigen for email communication, as both inbound and outbound mail flows may be interrupted while services remain in a crashed or unstable state. The lack of authentication requirement means that this disruption can be initiated by any internet-facing host with network connectivity to the vulnerable server ports.
In terms of industry classification standards, this vulnerability aligns closely with CWE-787: Out-of-bounds Write and CWE-400: Uncontrolled Resource Consumption, specifically manifesting as a stack exhaustion scenario often categorized under Denial of Service via resource exhaustion. From an offensive security framework perspective, such exploitation techniques are consistent with ATT&CK technique T1499: Endpoint Denial of Service, where the adversary aims to degrade or deny availability of target resources by consuming them in excessive amounts. The unauthenticated nature also touches upon CWE-287: Improper Authentication, as the system fails to verify identity before processing potentially destructive input structures that should be gated behind authentication checks for sensitive administrative interfaces like WebAdmin.
Mitigation strategies must prioritize immediate patching and network-level controls until updates are applied. Administrators should upgrade Axigen Mail Server to version 10.5.69, 10.6.40, or 10.7.2 or later, where the parsing logic has been hardened with strict depth limits for XML and JSON structures. In environments where immediate patching is not feasible, deploying a Web Application Firewall can help mitigate risk by inspecting incoming request bodies for abnormally deep nesting patterns before they reach the application parser. Additionally, restricting access to administrative interfaces like WebAdmin via IP whitelisting reduces the attack surface, although this does not protect public-facing services like standard webmail or SMTP listeners which remain vulnerable without a software update. Regular monitoring of service logs for sudden crashes or high CPU usage indicative of stack overflow events can also aid in early detection and response to potential exploitation attempts.