1 files changed, 42 insertions, 0 deletions
diff --git a/backport-CVE-2026-1642.patch b/backport-CVE-2026-1642.patch
new file mode 100644
index 0000000..5cd329c
--- /dev/null
+++ b/backport-CVE-2026-1642.patch
@@ -0,0 +1,42 @@
+From 784fa05025cb8cd0c770f99bc79d2794b9f85b6e Mon Sep 17 00:00:00 2001
+From: Roman Arutyunyan <arut@nginx.com>
+Date: Thu, 29 Jan 2026 13:27:32 +0400
+Subject: [PATCH] Upstream: detect premature plain text response from SSL
+ backend.
+
+When connecting to a backend, the connection write event is triggered
+first in most cases.  However if a response arrives quickly enough, both
+read and write events can be triggered together within the same event loop
+iteration.  In this case the read event handler is called first and the
+write event handler is called after it.
+
+SSL initialization for backend connections happens only in the write event
+handler since SSL handshake starts with sending Client Hello.  Previously,
+if a backend sent a quick plain text response, it could be parsed by the
+read event handler prior to starting SSL handshake on the connection.
+The change adds protection against parsing such responses on SSL-enabled
+connections.
+---
+ src/http/ngx_http_upstream.c | 9 +++++++++
+ 1 file changed, 9 insertions(+)
+
+diff --git a/src/http/ngx_http_upstream.c b/src/http/ngx_http_upstream.c
+index df577ad6721..cadc74479d4 100644
+--- a/src/http/ngx_http_upstream.c
++++ b/src/http/ngx_http_upstream.c
+@@ -2508,6 +2508,15 @@ ngx_http_upstream_process_header(ngx_http_request_t *r, ngx_http_upstream_t *u)
+             return;
+         }
+ 
++#if (NGX_HTTP_SSL)
++        if (u->ssl && c->ssl == NULL) {
++            ngx_log_error(NGX_LOG_ERR, c->log, 0,
++                          "upstream prematurely sent response");
++            ngx_http_upstream_next(r, u, NGX_HTTP_UPSTREAM_FT_ERROR);
++            return;
++        }
++#endif
++
+         u->state->bytes_received += n;
+ 
+         u->buffer.last += n;