FINDING 1
Nginx Buffer Overflow Vulnerability (CVE-2026-27654)
5.9
Risk Score
Affected Hosts
181.119.220.213
181.119.220.228
Vulnerability Description
ACME Security identified a heap-based buffer overflow vulnerability affecting the ngx_http_dav_module in NGINX Open Source and NGINX Plus. This vulnerability allows remote attackers to trigger a buffer overflow in the NGINX worker process, potentially resulting in worker process termination (denial of service) or unauthorized modification of source and destination file names outside the document root.
The vulnerability is exploitable when specific configuration conditions are met: the NGINX configuration must use the DAV module's MOVE or COPY methods in combination with prefix location and alias directives. While the integrity impact is constrained, successful exploitation leads to service disruption.
Remediation & Solution Strategy
ACME Consulting recommends taking the following corrective actions in order of priority:
1. Apply Vendor Patches
Upgrade all affected NGINX instances to the latest stable release provided by F5/NGINX to address the CVE-2026-27654 advisory directly at the source.
2. Configuration Mitigation (If patching is delayed)
Temporarily mitigate the risk by modifying NGINX configurations. Disable the
ngx_http_dav_module if it is not strictly required. If required, avoid using the alias directive in conjunction with DAV methods.
3. Web Application Firewall (WAF)
Ensure your perimeter WAF is configured to inspect and strictly validate the format and length of HTTP headers associated with WebDAV COPY and MOVE methods, blocking malformed requests.