CVE-2026-42934

A flaw was found in the ngx_http_charset_module module of NGINX. When charset, source_charset, charset_map and proxy_pass with disabled buffering ("off") directives are configured, an unauthenticated attacker can send crafted requests and cause a heap-based buffer over-read in the worker process, resulting in a limited disclosure of memory or a denial of service by forcing the process to restart.

To exploit this vulnerability, the charset, source_charset, charset_map and proxy_pass directives must be configured with disabled buffering, limiting its exposure as this is not the default configuration. Also, configurations that do not recode a UTF-8 response through charset_map are not vulnerable. This issue allows an attacker to have limited control to disclose memory content from the worker process or cause a denial of service by forcing the process to restart, but it cannot cause a complete system denial of service. Due to these reasons, this flaw has been rated with a moderate severity.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this vulnerability, enable proxy buffering (the default configuration).