CVE-2026-42055
HighCVSS 8.1Exploitation Probability (EPSS)
High risk85th percentile — higher than 85% of all known CVEs
Summary
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. It occurs when proxy_http_version 2 or grpc_pass directives are used for HTTP/2 proxying, ignore_invalid_headers is set to off, and large_client_header_buffers size exceeds 2 MB. A remote unauthenticated attacker can send large headers causing a heap-based buffer overflow in the NGINX worker process, leading to a restart or potential code execution.
Risk Assessment
The risk includes service disruption due to worker process restart and potential remote code execution on systems without ASLR or when ASLR is bypassed, which could lead to full server compromise.
Recommendation
Immediately update NGINX to the latest patched version. As a workaround, set ignore_invalid_headers to on or reduce large_client_header_buffers size to 2 MB or less.
Original NVD description (English source)
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules. This vulnerability exists when the proxy_http_version to 2 or grpc_pass directives are used to proxy HTTP/2 traffic, the ignore_invalid_headers directive is set to off, and the large_client_header_buffers directive size is larger than 2 megabytes. A remote, unauthenticated attacker, along with conditions beyond their control, could send large headers while creating an upstream request. This may cause a heap-based buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.