CVE-2026-48187: OTRS Email Handler Denial of Service – Uncontrolled Resource Allocation

Technical summary

CVE-2026-48187 stems from uncontrolled resource allocation without rate limiting or quota enforcement in OTRS's email processing pipeline. The vulnerability is rooted in CWE-400 (Uncontrolled Resource Consumption) and CWE-770 (Allocation of Resources Without Limits or Throttling). An authenticated user can craft email interactions that force the OTRS web server to allocate memory or processing resources excessively, leading to resource exhaustion and potential service interruption. The CVSS 3.1 score of 5.7 reflects a network-accessible, low-complexity attack requiring login credentials and user interaction, with high availability impact but no confidentiality or integrity compromise.

Business impact

Organizations using affected OTRS versions face potential disruption to their ticket management and customer support workflows. If the web server becomes unavailable due to resource exhaustion, support staff cannot access, create, or manage tickets, directly impacting customer service delivery. The attack requires valid credentials, limiting the threat to insider scenarios or compromised accounts. Recovery typically requires manual server restart, introducing operational overhead. For businesses where OTRS is mission-critical, this vulnerability poses a moderate operational risk that should be addressed promptly to prevent support-related incidents.

Affected systems

OTRS versions 8.0.x, 2023.x, 2024.x, 2025.x, and 2026.x before 2026.4.x are confirmed affected. Additionally, OTRS Community Edition 6.x and 7.x, as well as products derived from OTRS Community Edition, are likely vulnerable. Organizations should verify their exact OTRS version and deployment model (Community vs. hosted editions) against vendor guidance to determine exposure. Check your OTRS admin interface or deployment documentation for the precise version number.

Exploitability

Exploitation requires valid OTRS login credentials and relies on user interaction (CWE-770 vector component: PR:L, UI:R), reducing the immediate threat from anonymous attacks. An attacker with a legitimate account or one obtained through credential compromise could trigger the vulnerability by sending specially crafted emails or interacting with the email handling system in a way that triggers excessive resource allocation. The low attack complexity and network accessibility mean that once credentials are obtained, exploitation is straightforward. This is not currently tracked in the CISA KEV catalog, suggesting active exploitation is not yet widespread, but the attack surface remains present for any organization with internal or compromised user access.

Remediation

OTRS has released patches in version 2026.4.x and later that implement resource allocation limits and throttling in the email handling subsystem. Organizations should prioritize upgrading to a patched version as soon as feasible. If immediate patching is not possible, consider implementing network-level or application-level controls to monitor email processing load and restrict email submission rates. Additionally, review OTRS user access policies and credential management to minimize the risk of unauthorized account compromise that could be used to trigger this vulnerability.

Patch guidance

Verify the availability of patched versions from the OTRS vendor advisory. Organizations running 2026.x versions should update to 2026.4.x or later. Users on 2025.x, 2024.x, 2023.x, or 8.0.x should consult the OTRS security advisory for patch availability specific to their branch. Community Edition users (6.x, 7.x) should check the OTRS community repository for available patches or consider upgrading to a supported commercial version. Test patches in a non-production environment first to ensure compatibility with existing configurations and integrations before deploying to production systems.

Detection guidance

Monitor OTRS web server resource utilization during normal operations to establish a baseline for memory and CPU consumption. Alert on sudden spikes in resource usage correlated with email processing activities. Examine OTRS logs for unusual patterns in email submissions or processing, particularly from specific user accounts. Check web server error logs for signs of process termination or resource exhaustion warnings. Implement rate limiting on email submission endpoints if supported by your OTRS deployment. Network monitoring for abnormal email volumes from authenticated sessions may also help identify exploitation attempts. Correlate these signals with authentication logs to identify potentially compromised accounts.

Why prioritize this

Although rated MEDIUM severity with a CVSS of 5.7, this vulnerability should be prioritized for timely remediation because it directly impacts service availability and requires only basic authentication to exploit. Organizations where OTRS is a critical service delivery component should treat this with higher priority to prevent support ticket system outages. The lack of KEV listing and low active exploitation baseline provide a window to patch before widespread abuse. Prioritization should reflect your organization's dependency on OTRS uptime and the likelihood of internal threat vectors (insider risk or credential compromise).

Risk score, explained

The CVSS 3.1 score of 5.7 (MEDIUM) is driven by: (1) Network accessibility and low attack complexity, which increase ease of exploitation; (2) requirement for authenticated access (PR:L) and user interaction (UI:R), which limit the threat to credentialed insiders or compromised accounts; (3) high availability impact (A:H) reflecting the denial-of-service outcome; and (4) no confidentiality or integrity impact (C:N, I:N), as the vulnerability only affects system availability. The overall medium rating balances the serious availability impact against the credential and interaction requirements that limit exposure.

Frequently asked questions