CVE-2026-42055

Name	CVE-2026-42055
Description	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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
nginx (PTS)	bullseye	1.18.0-6.1+deb11u3	vulnerable
	bullseye (security)	1.18.0-6.1+deb11u7	vulnerable
	bookworm	1.22.1-9+deb12u6	vulnerable
	bookworm (security)	1.22.1-9+deb12u8	vulnerable
	trixie	1.26.3-3+deb13u4	vulnerable
	trixie (security)	1.26.3-3+deb13u6	vulnerable
	forky, sid	1.30.1-4	vulnerable

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
nginx	source	(unstable)	(unfixed)

Notes

https://my.f5.com/manage/s/article/K000161584
https://github.com/nginx/nginx/commit/58a7bc3406ac8b9dc0e0afafc69ba42df56009e3 (master)
https://github.com/nginx/nginx/commit/26d824ec3a2f819300edce0ab3b055751c9843ff (release-1.31.2)
https://github.com/nginx/nginx/commit/131be8514da8985b15b74150521afedbf9cc4ea3 (release-1.30.3)