CVE-2026-56845 Rocket.Chat CVE debrief

Who should care

Defenders and security teams responsible for configuring and securing CustomSounds storage should assess exposure and implement compensating controls. This includes reviewing and updating incident response plans, conducting thorough reviews of affected systems and their configurations, and developing plans to address potential data breaches and unauthorized access. Additionally, security teams should review and update security policies and procedures to

Why it matters

CVE-2026-56845 is a high-severity LFI vulnerability in CustomSounds storage, allowing unauthenticated attacks. Defenders should assess exposure, implement compensating controls, and monitor for potential exploitation attempts.

• Potential data breaches due to arbitrary file reading
• Need for verification of exposure and compensating controls
• Potential impact on incident response plans

Technical summary

The vulnerability exists under /custom-sounds/ when CustomSounds storage is configured to FileSystem, allowing an attacker to read arbitrary files outside the base directory by including ../ sequences in the request path. This is due to insufficient input validation and sanitization in the /custom-sounds/ endpoint. The vulnerability has significant implications for defenders and security teams responsible for configuring and securing CustomSounds storage. They should assess exposure and implement compensating controls to mitigate potential risks.

Defensive priority

Defenders should prioritize verifying exposure and implementing compensating controls, as the vulnerability allows for potential data breaches.

Recommended defensive actions

• Verify if CustomSounds storage is configured to FileSystem and assess exposure
• Implement compensating controls, such as restricting access to /custom-sounds/
• Monitor for potential exploitation attempts
• Review and update incident response plans
• Conduct a thorough review of the affected system and its configurations
• Develop a plan to address potential data breaches and unauthorized access
• Review and update security policies and procedures

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but additional information on affected versions, exploitation, and remediation is limited. The vulnerability has been publicly disclosed, and defenders should verify exposure and implement compensating controls. The CVE Program and NVD provide official records and assessments of the vulnerability, but further research is needed to understand the full scope of the issue.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.