CVE-2022-36074 is a medium-severity vulnerability affecting Nextcloud Server, an open-source personal cloud platform widely used for file sharing and collaboration. The vulnerability arises from improper handling of the Authorization HTTP header during protocol downgrade scenarios. Specifically, when a client connection is downgraded from HTTPS to HTTP, the Nextcloud server fails to strip the Authorization header, which contains sensitive authentication tokens. This flaw can lead to exposure of these credentials to unauthorized actors, potentially allowing them to access user accounts without proper authentication. The affected versions include all Nextcloud Server releases prior to 23.0.7 and versions from 24.0.0 up to but not including 24.0.3. Similarly, Nextcloud Enterprise Server versions prior to 22.2.11, 23.0.7, and 24.0.3 are vulnerable. There are no known workarounds, making timely patching critical. The vulnerability is classified under CWE-200, indicating exposure of sensitive information to unauthorized parties. Although no exploits have been observed in the wild, the nature of the vulnerability means that an attacker capable of inducing an HTTP downgrade or intercepting downgraded traffic could capture authorization headers and compromise user accounts. This could lead to unauthorized access, data leakage, and potential further exploitation within affected environments. The vulnerability highlights the importance of strict enforcement of secure transport protocols and proper header sanitization in web applications handling sensitive authentication data.

For European organizations, the impact of CVE-2022-36074 can be significant, especially for those relying on Nextcloud for internal file sharing, collaboration, and cloud storage. Unauthorized access resulting from this vulnerability could lead to exposure of confidential business documents, intellectual property, and personal data protected under GDPR. This could result in regulatory penalties, reputational damage, and operational disruption. Organizations in sectors such as finance, healthcare, government, and critical infrastructure, which often use Nextcloud for secure collaboration, are particularly at risk. The vulnerability could also facilitate lateral movement within networks if attackers leverage compromised credentials to escalate privileges. Since Nextcloud is often deployed in hybrid or on-premises environments, the risk is heightened in cases where network segmentation or HTTPS enforcement is weak, allowing attackers to force HTTP downgrade attacks or intercept downgraded traffic. The absence of known exploits in the wild reduces immediate risk but does not eliminate the threat, especially as attackers may develop exploits targeting this vulnerability. Overall, the vulnerability poses a medium risk but with potential for high impact in sensitive environments.

1. Immediate upgrade of Nextcloud Server and Enterprise Server to the fixed versions: 23.0.7, 24.0.3, or 22.2.11 for Enterprise, as applicable. 2. Enforce strict HTTPS usage by disabling HTTP access entirely or redirecting all HTTP traffic to HTTPS to prevent downgrade attacks. 3. Implement network-level protections such as HTTP Strict Transport Security (HSTS) headers to instruct clients to only use HTTPS. 4. Use network monitoring and intrusion detection systems to identify unusual downgrade attempts or unauthorized access patterns. 5. Review and harden proxy and load balancer configurations to ensure they do not inadvertently downgrade HTTPS connections or leak Authorization headers. 6. Conduct internal audits of Nextcloud deployments to verify that no legacy or vulnerable versions remain in use. 7. Educate users on the risks of using unsecured networks and the importance of verifying secure connections when accessing Nextcloud services. 8. Consider deploying additional authentication mechanisms such as multi-factor authentication (MFA) to reduce the impact of credential exposure. 9. Regularly review Nextcloud security advisories and apply patches promptly to mitigate emerging threats.