CVE-2026-42055
HighCVSS 8.1Exploitation Probability (EPSS)
Very high risk90th percentile - higher than 90% of all known CVEs
Summary
Heap-based buffer overflow in NGINX ngx_http_proxy_v2_module and ngx_http_grpc_module. Specific configuration conditions and large headers can cause NGINX worker process crash, and in some cases allow code execution.
Risk Assessment
An attacker can remotely crash the NGINX server (DoS) or potentially execute code if ASLR is disabled or bypassable.
Recommendation
Update NGINX to a patched version and avoid configurations with large header buffers when proxying HTTP/2.
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.