Critical [CVE-2026-42055] NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_proxy_v2_module and ngx_http_grpc_module modules
This critical-severity F5 advisory covers CVE-2026-42055 affecting NGINX Open Source, NGINX Plus.
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Summary
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.
- NGINX Open Source 1.13.10 before 1.31.2
- NGINX Open Source 1.30.2 before 1.30.3
- NGINX Plus 37.0 before 37.0.2.1
- NGINX Plus R36 before R36 P6
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
- 1.31.2
- 1.30.3
- 37.0.2.1
- R36 P6
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
Mitigation
Upgrade to a fixed release: 1.31.2, 1.30.3, 37.0.2.1, R36 P6. That is the remediation for this advisory.
The vendor advisory may list additional interim mitigations or workarounds not captured here — review it before change work.
Official advisory · high-confidence parse· fetched 2 months ago·verify at source
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