CVE-2026-24044 is a vulnerability classified under CWE-336 (Same Seed in PRNG) affecting the Element Server Suite Community Edition (ESS Community) Helm Chart used to deploy Matrix stacks on Kubernetes. The vulnerability arises from an insecure key generation method in the secrets initialization hook of the Helm Chart (using the matrix-tools container before version 0.5.7). Specifically, when initSecrets.enabled is not disabled and synapse.signingKey is undefined, the server key pair is generated using a predictable seed in the PRNG. This predictability allows a remote network attacker to recreate the same server key pair, effectively impersonating the legitimate Matrix server. Since the server key authenticates requests and events originating from the server, an attacker with the key can forge events, manipulate room states, and disrupt communication integrity and availability. However, end-to-end encrypted room conversations remain confidential as their encryption keys are not compromised by this vulnerability. The vulnerability has a CVSS 4.0 base score of 9.2 (critical), reflecting its severe impact on confidentiality, integrity, and availability, despite requiring high attack complexity and no privileges or user interaction. The fix was implemented in matrix-tools 0.5.7, released as part of ESS Community Helm Chart 25.12.1, which uses a secure key generation method to prevent predictable key pairs.

For European organizations deploying Matrix communication infrastructure using the ESS Community Helm Chart versions prior to 25.12.1, this vulnerability poses a significant risk. Attackers on the same network or with network access can impersonate legitimate Matrix servers, enabling them to inject malicious events, disrupt room communications, and potentially cause denial of service or misinformation within collaborative environments. This undermines trust in internal and external communications, affecting operational continuity and data integrity. Although past end-to-end encrypted messages remain secure, ongoing communications and room states are vulnerable. Given the increasing adoption of Matrix-based collaboration tools in Europe, especially in sectors like government, finance, and critical infrastructure, the impact could be substantial. The vulnerability could facilitate espionage, sabotage, or misinformation campaigns targeting European organizations relying on Matrix for secure communication.

European organizations should immediately upgrade their ESS Community Helm Chart deployments to version 25.12.1 or later, which includes matrix-tools 0.5.7 with the secure key generation fix. Administrators should verify that initSecrets.enabled is not set to false and that synapse.signingKey is explicitly defined to avoid fallback to insecure key generation. Additionally, organizations should audit existing server keys for potential compromise and consider rotating keys post-upgrade. Network segmentation and strict access controls should be enforced to limit exposure of Matrix servers to untrusted networks. Monitoring for anomalous server behavior or unexpected event injections can help detect exploitation attempts. Finally, organizations should maintain up-to-date backups of room states and configurations to enable recovery in case of disruption.