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Fix CVE-2026-42945 Buffer overrun in rewrite module via arguments in replacement strings

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This commit is contained in:
Jonathan Wright 2026-05-13 15:10:47 -05:00
parent b0c2ccf12f
commit 75698c0d6b
2 changed files with 51 additions and 1 deletions
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42
SOURCES/0019-Rewrite-fixed-escaping-and-possible-buffer-overrun.patch Normal file
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@ -0,0 +1,42 @@
From 524977e7c534e87e5b55739fa74601c9f1102686 Mon Sep 17 00:00:00 2001
From: Roman Arutyunyan <arut@nginx.com>
Date: Wed, 22 Apr 2026 09:39:31 +0400
Subject: [PATCH] Rewrite: fixed escaping and possible buffer overrun
The following code resulted in incorrect escaping of $1 and possible
segfault:
location / {
rewrite ^(.*) /new?c=1;
set $myvar $1;
return 200 $myvar;
}
If there were arguments in a rewrite's replacement string, the is_args flag
was set and incorrectly never cleared. This resulted in escaping applied
to any captures evaluated afterwards in set or if. Additionally buffer was
allocated by ngx_http_script_complex_value_code() without escaping expected,
thus this also resulted in buffer overrun and possible segfault.
A similar issue was fixed in 74d939974d43.
Reported by Leo Lin.
---
src/http/ngx_http_script.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/src/http/ngx_http_script.c b/src/http/ngx_http_script.c
index a2b9f1b7bf..2ea6113735 100644
--- a/src/http/ngx_http_script.c
+++ b/src/http/ngx_http_script.c
@@ -1202,6 +1202,7 @@ ngx_http_script_regex_end_code(ngx_http_script_engine_t *e)
r = e->request;
+ e->is_args = 0;
e->quote = 0;
ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
--
2.53.0

10
SPECS/nginx.spec
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@ -41,7 +41,7 @@
Name: nginx
Epoch: 2
Version: 1.20.1
Release: 24%{?dist}.2.alma.1
Release: 24%{?dist}.2.alma.2
Summary: A high performance web server and reverse proxy server
# BSD License (two clause)
@ -135,6 +135,10 @@ Patch17: 0017-Mail-fixed-clearing-s-passwd-in-auth-http-requests.patch
# upstream patch - https://github.com/nginx/nginx/commit/7725c372c2f
Patch18: 0018-Mp4-avoid-zero-size-buffers-in-output.patch
# CVE-2026-42945
# upstream patch - https://github.com/nginx/nginx/commit/524977e7c534e87e5b55739fa74601c9f1102686
Patch19: 0019-Rewrite-fixed-escaping-and-possible-buffer-overrun.patch
BuildRequires: make
BuildRequires: gcc
BuildRequires: gnupg2
@ -644,6 +648,10 @@ fi
%changelog
* Wed May 13 2026 Jonathan Wright <jonathan@almalinux.org> - 2:1.20.1-24.2.alma.2
- Fix CVE-2026-42945 nginx: NGINX: Buffer overrun in rewrite module via
arguments in replacement strings
* Fri Apr 10 2026 Eduard Abdullin <eabdullin@almalinux.org> - 2:1.20.1-24.2.alma.1
- Debrand for AlmaLinux