File CVE-2025-47911.patch of Package google-osconfig-agent

From c217fe54b033f05ca89b931c1650738a68914f30 Mon Sep 17 00:00:00 2001
From: Roland Shoemaker <roland@golang.org>
Date: Mon, 29 Sep 2025 16:33:18 -0700
Subject: [PATCH 2/2] html: impose open element stack size limit

The HTML specification contains a number of algorithms which are
quadratic in complexity by design. Instead of adding complicated
workarounds to prevent these cases from becoming extremely expensive in
pathological cases, we impose a limit of 512 to the size of the stack of
open elements. It is extremely unlikely that non-adversarial HTML
documents will ever hit this limit (but if we see cases of this, we may
want to make the limit configurable via a ParseOption).

Thanks to Guido Vranken and Jakub Ciolek for both independently
reporting this issue.

Fixes CVE-2025-47911
Fixes golang/go#75682

Change-Id: I890517b189af4ffbf427d25d3fde7ad7ec3509ad
Reviewed-on: https://go-review.googlesource.com/c/net/+/709876
Reviewed-by: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
---
 html/escape.go |  2 +-
 html/parse.go  | 21 +++++++++++++++++----
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/html/escape.go b/html/escape.go
index 04c6bec..12f2273 100644
--- a/html/escape.go
+++ b/html/escape.go
@@ -299,7 +299,7 @@ func escape(w writer, s string) error {
 		case '\r':
 			esc = "&#13;"
 		default:
-			panic("unrecognized escape character")
+			panic("html: unrecognized escape character")
 		}
 		s = s[i+1:]
 		if _, err := w.WriteString(esc); err != nil {
diff --git a/html/parse.go b/html/parse.go
index 722e927..88fc005 100644
--- a/html/parse.go
+++ b/html/parse.go
@@ -231,7 +231,14 @@ func (p *parser) addChild(n *Node) {
 	}
 
 	if n.Type == ElementNode {
-		p.oe = append(p.oe, n)
+		p.insertOpenElement(n)
+	}
+}
+
+func (p *parser) insertOpenElement(n *Node) {
+	p.oe = append(p.oe, n)
+	if len(p.oe) > 512 {
+		panic("html: open stack of elements exceeds 512 nodes")
 	}
 }
 
@@ -810,7 +817,7 @@ func afterHeadIM(p *parser) bool {
 			p.im = inFramesetIM
 			return true
 		case a.Base, a.Basefont, a.Bgsound, a.Link, a.Meta, a.Noframes, a.Script, a.Style, a.Template, a.Title:
-			p.oe = append(p.oe, p.head)
+			p.insertOpenElement(p.head)
 			defer p.oe.remove(p.head)
 			return inHeadIM(p)
 		case a.Head:
@@ -2324,9 +2331,13 @@ func (p *parser) parseCurrentToken() {
 	}
 }
 
-func (p *parser) parse() error {
+func (p *parser) parse() (err error) {
+	defer func() {
+		if panicErr := recover(); panicErr != nil {
+			err = fmt.Errorf("%s", panicErr)
+		}
+	}()
 	// Iterate until EOF. Any other error will cause an early return.
-	var err error
 	for err != io.EOF {
 		// CDATA sections are allowed only in foreign content.
 		n := p.oe.top()
@@ -2355,6 +2366,8 @@ func (p *parser) parse() error {
 // <tag>s. Conversely, explicit <tag>s in r's data can be silently dropped,
 // with no corresponding node in the resulting tree.
 //
+// Parse will reject HTML that is nested deeper than 512 elements.
+//
 // The input is assumed to be UTF-8 encoded.
 func Parse(r io.Reader) (*Node, error) {
 	return ParseWithOptions(r)
-- 
2.51.0