From c91a75c2c8778a9a8343c6bb4fa89eb1f978059f Mon Sep 17 00:00:00 2001
From: Julien Cretel <jub0bsinthecloud@gmail.com>
Date: Mon, 10 Nov 2025 21:59:25 +0100
Subject: [PATCH] mime: parse media types that contain braces

This CL fixes a bug introduced by CL 666655: isTokenChar would no longer
(but should) report true for '{' and '}'.

Fixes #76236
---
 src/mime/grammar.go        | 2 ++
 src/mime/mediatype_test.go | 3 +++
 2 files changed, 5 insertions(+)

diff --git a/src/mime/grammar.go b/src/mime/grammar.go
index cc578fbcfd4168..1efd8a16dec607 100644
--- a/src/mime/grammar.go
+++ b/src/mime/grammar.go
@@ -62,7 +62,9 @@ func isTokenChar(c byte) bool {
 		1<<'^' |
 		1<<'_' |
 		1<<'`' |
+		1<<'{' |
 		1<<'|' |
+		1<<'}' |
 		1<<'~'
 	return ((uint64(1)<<c)&(mask&(1<<64-1)) |
 		(uint64(1)<<(c-64))&(mask>>64)) != 0
diff --git a/src/mime/mediatype_test.go b/src/mime/mediatype_test.go
index 251df8d6691ab9..da8d64de7a3f0c 100644
--- a/src/mime/mediatype_test.go
+++ b/src/mime/mediatype_test.go
@@ -413,6 +413,9 @@ func init() {
 		// Issue #48866: duplicate parameters containing equal values should be allowed
 		{`text; charset=utf-8; charset=utf-8; format=fixed`, "text", m("charset", "utf-8", "format", "fixed")},
 		{`text; charset=utf-8; format=flowed; charset=utf-8`, "text", m("charset", "utf-8", "format", "flowed")},
+
+		// Issue #76236: '{' and '}' are token chars.
+		{"attachment; filename={file}.png", "attachment", m("filename", "{file}.png")},
 	}
 }