nginx: fix CVE-2026-56434

This patch applies the upstream fix as referenced in [2],
using the commit shown in [1].

[1] https://github.com/nginx/nginx/commit/ddde692db11ab8238e9ca661007f64c9f6d764d2
[2] https://nginx.org/en/security_advisories.html

Signed-off-by: Hetvi Thakar <hthakar@cisco.com>
Signed-off-by: Anuj Mittal <anuj.mittal@oss.qualcomm.com>

meta-webserver/recipes-httpd/nginx/files/CVE-2026-56434.patch

@@ -0,0 +1,71 @@
+From ddde692db11ab8238e9ca661007f64c9f6d764d2 Mon Sep 17 00:00:00 2001
+From: Roman Arutyunyan <arut@nginx.com>
+Date: Mon, 29 Jun 2026 21:49:27 +0400
+Subject: [PATCH] Avoid duplicate subrequest finalization
+
+Previously, if a subrequest was posted twice, it could be finalized in
+both calls, excessively reducing r->main->count and potentially leading
+to a use-after-free.
+
+The fix is to avoid posting a request if it's already posted.  Also,
+as a hardening measure, r->write_event_handler is now reset to a no-op
+handler during active subrequest finalization.
+
+The problem manifests itself in ngx_http_ssi_filter_module during
+unbuffered proxying.  If a subrequest is created for an SSI include
+statement while the main request has some data postponed by another
+include, this subrequest becomes double-posted when the main request
+data is flushed.  The first post comes from ngx_http_subrequest() and
+the second one comes from ngx_http_postpone_filter().  In case of a
+quick subrequest finalization, the above mentioned problem happens.
+
+Reported by P4P3R-HAK.
+
+CVE: CVE-2026-56434
+Upstream-Status: Backport [https://github.com/nginx/nginx/commit/ddde692db11ab8238e9ca661007f64c9f6d764d2]
+
+(cherry picked from commit ddde692db11ab8238e9ca661007f64c9f6d764d2)
+Signed-off-by: Hetvi Thakar <hthakar@cisco.com>
+---
+ src/http/ngx_http_request.c | 12 ++++++++++--
+ 1 file changed, 10 insertions(+), 2 deletions(-)
+
+diff --git a/src/http/ngx_http_request.c b/src/http/ngx_http_request.c
+index ceac8d307..6dc275757 100644
+--- a/src/http/ngx_http_request.c
++++ b/src/http/ngx_http_request.c
+@@ -2501,6 +2501,14 @@ ngx_http_post_request(ngx_http_request_t *r, ngx_http_posted_request_t *pr)
+ {
+     ngx_http_posted_request_t  **p;
+ 
++    for (p = &r->main->posted_requests; *p; p = &(*p)->next) {
++        if ((*p)->request == r) {
++            ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
++                           "http request already posted");
++            return NGX_OK;
++        }
++    }
++
+     if (pr == NULL) {
+         pr = ngx_palloc(r->pool, sizeof(ngx_http_posted_request_t));
+         if (pr == NULL) {
+@@ -2511,8 +2519,6 @@ ngx_http_post_request(ngx_http_request_t *r, ngx_http_posted_request_t *pr)
+     pr->request = r;
+     pr->next = NULL;
+ 
+-    for (p = &r->main->posted_requests; *p; p = &(*p)->next) { /* void */ }
+-
+     *p = pr;
+ 
+     return NGX_OK;
+@@ -2632,6 +2638,8 @@ ngx_http_finalize_request(ngx_http_request_t *r, ngx_int_t rc)
+ 
+             r->main->count--;
+ 
++            r->write_event_handler = ngx_http_request_empty_handler;
++
+             if (pr->postponed && pr->postponed->request == r) {
+                 pr->postponed = pr->postponed->next;
+             }
+-- 
+2.35.6

meta-webserver/recipes-httpd/nginx/nginx_1.28.3.bb

@@ -14,6 +14,7 @@ SRC_URI:append = " \
     file://CVE-2026-42533_p3.patch \
     file://CVE-2026-42533_p4.patch \
     file://CVE-2026-42533_p5.patch \
+    file://CVE-2026-56434.patch \
 "
 
 LIC_FILES_CHKSUM = "file://LICENSE;md5=3dc49537b08b14c8b66ad247bb4c4593"

meta-webserver/recipes-httpd/nginx/nginx_1.29.7.bb

@@ -14,6 +14,7 @@ SRC_URI:append = " \
     file://CVE-2026-42533_p3.patch \
     file://CVE-2026-42533_p4.patch \
     file://CVE-2026-42533_p5.patch \
+    file://CVE-2026-56434.patch \
 "
 
 # 1.28.x branch is the current stable branch, the recommended default