diff --git a/patches/021-backport-reject-bare-chunked.patch b/patches/021-backport-reject-bare-chunked.patch
new file mode 100644
index 0000000000..c7831e4e4d
--- /dev/null
+++ b/patches/021-backport-reject-bare-chunked.patch
@@ -0,0 +1,160 @@
+From 15e01a2e43ecb8c7e15ff7e9d62fe3f10dcac931 Mon Sep 17 00:00:00 2001
+From: Damien Neil <dneil@google.com>
+Date: Wed, 26 Feb 2025 13:40:00 -0800
+Subject: [PATCH] [release-branch.go1.23] net/http: reject newlines in chunk-size lines
+
+Unlike request headers, where we are allowed to leniently accept
+a bare LF in place of a CRLF, chunked bodies must always use CRLF
+line terminators. We were already enforcing this for chunk-data lines;
+do so for chunk-size lines as well. Also reject bare CRs anywhere
+other than as part of the CRLF terminator.
+
+Fixes CVE-2025-22871
+Fixes #72010
+For #71988
+
+Change-Id: Ib0e21af5a8ba28c2a1ca52b72af8e2265ec79e4a
+Reviewed-on: https://go-review.googlesource.com/c/go/+/652998
+Reviewed-by: Jonathan Amsterdam <jba@google.com>
+LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
+(cherry picked from commit d31c805535f3fde95646ee4d87636aaaea66847b)
+Reviewed-on: https://go-review.googlesource.com/c/go/+/657216
+---
+
+diff --git a/src/net/http/internal/chunked.go b/src/net/http/internal/chunked.go
+index 196b5d8..0b08a97 100644
+--- a/src/net/http/internal/chunked.go
++++ b/src/net/http/internal/chunked.go
+@@ -164,6 +164,19 @@
+ 		}
+ 		return nil, err
+ 	}
++
++	// RFC 9112 permits parsers to accept a bare \n as a line ending in headers,
++	// but not in chunked encoding lines. See https://www.rfc-editor.org/errata/eid7633,
++	// which explicitly rejects a clarification permitting \n as a chunk terminator.
++	//
++	// Verify that the line ends in a CRLF, and that no CRs appear before the end.
++	if idx := bytes.IndexByte(p, '\r'); idx == -1 {
++		return nil, errors.New("chunked line ends with bare LF")
++	} else if idx != len(p)-2 {
++		return nil, errors.New("invalid CR in chunked line")
++	}
++	p = p[:len(p)-2] // trim CRLF
++
+ 	if len(p) >= maxLineLength {
+ 		return nil, ErrLineTooLong
+ 	}
+@@ -171,14 +184,14 @@
+ }
+ 
+ func trimTrailingWhitespace(b []byte) []byte {
+-	for len(b) > 0 && isASCIISpace(b[len(b)-1]) {
++	for len(b) > 0 && isOWS(b[len(b)-1]) {
+ 		b = b[:len(b)-1]
+ 	}
+ 	return b
+ }
+ 
+-func isASCIISpace(b byte) bool {
+-	return b == ' ' || b == '\t' || b == '\n' || b == '\r'
++func isOWS(b byte) bool {
++	return b == ' ' || b == '\t'
+ }
+ 
+ var semi = []byte(";")
+diff --git a/src/net/http/internal/chunked_test.go b/src/net/http/internal/chunked_test.go
+index af79711..312f173 100644
+--- a/src/net/http/internal/chunked_test.go
++++ b/src/net/http/internal/chunked_test.go
+@@ -280,6 +280,33 @@
+ 	}
+ }
+ 
++func TestChunkInvalidInputs(t *testing.T) {
++	for _, test := range []struct {
++		name string
++		b    string
++	}{{
++		name: "bare LF in chunk size",
++		b:    "1\na\r\n0\r\n",
++	}, {
++		name: "extra LF in chunk size",
++		b:    "1\r\r\na\r\n0\r\n",
++	}, {
++		name: "bare LF in chunk data",
++		b:    "1\r\na\n0\r\n",
++	}, {
++		name: "bare LF in chunk extension",
++		b:    "1;\na\r\n0\r\n",
++	}} {
++		t.Run(test.name, func(t *testing.T) {
++			r := NewChunkedReader(strings.NewReader(test.b))
++			got, err := io.ReadAll(r)
++			if err == nil {
++				t.Fatalf("unexpectedly parsed invalid chunked data:\n%q", got)
++			}
++		})
++	}
++}
++
+ type funcReader struct {
+ 	f   func(iteration int) ([]byte, error)
+ 	i   int
+diff --git a/src/net/http/serve_test.go b/src/net/http/serve_test.go
+index b2858ba..2543935 100644
+--- a/src/net/http/serve_test.go
++++ b/src/net/http/serve_test.go
+@@ -7284,3 +7284,52 @@
+ 	readyc <- struct{}{} // server starts reading from the request body
+ 	readyc <- struct{}{} // server finishes reading from the request body
+ }
++
++func TestInvalidChunkedBodies(t *testing.T) {
++	for _, test := range []struct {
++		name string
++		b    string
++	}{{
++		name: "bare LF in chunk size",
++		b:    "1\na\r\n0\r\n\r\n",
++	}, {
++		name: "bare LF at body end",
++		b:    "1\r\na\r\n0\r\n\n",
++	}} {
++		t.Run(test.name, func(t *testing.T) {
++			reqc := make(chan error)
++			ts := newClientServerTest(t, http1Mode, HandlerFunc(func(w ResponseWriter, r *Request) {
++				got, err := io.ReadAll(r.Body)
++				if err == nil {
++					t.Logf("read body: %q", got)
++				}
++				reqc <- err
++			})).ts
++
++			serverURL, err := url.Parse(ts.URL)
++			if err != nil {
++				t.Fatal(err)
++			}
++
++			conn, err := net.Dial("tcp", serverURL.Host)
++			if err != nil {
++				t.Fatal(err)
++			}
++
++			if _, err := conn.Write([]byte(
++				"POST / HTTP/1.1\r\n" +
++					"Host: localhost\r\n" +
++					"Transfer-Encoding: chunked\r\n" +
++					"Connection: close\r\n" +
++					"\r\n" +
++					test.b)); err != nil {
++				t.Fatal(err)
++			}
++			conn.(*net.TCPConn).CloseWrite()
++
++			if err := <-reqc; err == nil {
++				t.Errorf("server handler: io.ReadAll(r.Body) succeeded, want error")
++			}
++		})
++	}
++}