diff --git a/backport-CVE-2021-27135.patch b/backport-CVE-2021-27135.patch
new file mode 100644
index 0000000..cfc7f34
--- /dev/null
+++ b/backport-CVE-2021-27135.patch
@@ -0,0 +1,52 @@
+From 82ba55b8f994ab30ff561a347b82ea340ba7075c Mon Sep 17 00:00:00 2001
+From: "Thomas E. Dickey" <dickey@invisible-island.net>
+Date: Tue, 9 Feb 2021 23:04:41 +0000
+Subject: [PATCH] snapshot of project "xterm", label xterm-365d
+
+--- a/button.c
++++ b/button.c
+@@ -3669,6 +3669,7 @@
+ {
+     TScreen *screen = TScreenOf(xw);
+     int i, j = 0;
++    size_t have = 0;
+     int eol;
+     Char *line;
+     Char *lp;
+@@ -3695,7 +3696,11 @@
+ 
+     /* UTF-8 may require more space */
+     if_OPT_WIDE_CHARS(screen, {
+-	j *= 4;
++      if (j > 0) {
++        if (screen->max_combining > 0)
++          j += screen->max_combining;
++        j *= 6;
++      }
+     });
+ 
+     /* now get some memory to save it in */
+@@ -3732,10 +3737,20 @@
+     }
+     *lp = '\0';			/* make sure we have end marked */
+ 
+-    TRACE(("Salted TEXT:%d:%s\n", (int) (lp - line),
+-	   visibleChars(line, (unsigned) (lp - line))));
++    have = (size_t) (lp - line);
++    /*
++     * Scanning the buffer twice is unnecessary.  Discard unwanted memory if
++     * the estimate is too-far off.
++     */
++     if ((have * 2) < (size_t) j) {
++       screen->selection_size = have + 1;
++       line = realloc(line, screen->selection_size);
++     }
+ 
+-    screen->selection_length = (unsigned long) (lp - line);
++    TRACE(("Salted TEXT:%d:%s\n", (int) have,
++      visibleChars(line, (unsigned) have)));
++
++    screen->selection_length = (unsigned long) have;
+ }
+ 
+ #if OPT_PASTE64
diff --git a/xterm.spec b/xterm.spec
index 0733d1f..0460a7a 100644
--- a/xterm.spec
+++ b/xterm.spec
@@ -1,11 +1,13 @@
 Name:		xterm
 Version:	334
-Release:        4
+Release:        5
 Summary:	It is a terminal emulator for the X Window System
 License:	MIT
 URL:		http://invisible-island.net/xterm
 Source0:	http://invisible-island.net/xterm/xterm-334.tgz
 
+Patch6000:      backport-CVE-2021-27135.patch
+
 BuildRequires: 	gcc git pkgconfig ncurses-devel libutempter-devel
 BuildRequires: 	libXft-devel libXaw-devel libXext-devel desktop-file-utils
 BuildRequires: 	libxkbfile-devel xorg-x11-apps
@@ -62,6 +64,9 @@ install -m 644 -p xterm.appdata.xml %{buildroot}/%{_datadir}/appdata
 %{_mandir}/man1/*
 
 %changelog
+* Wed Mar 03 2021 jinzhimin <jinzhimin2@huawei.com> - 334-5
+- fix CVE-2021-27135
+
 * Thu Jan 3 2020 openEuler Buildteam <buildteam@openeuler.org> - 334-4
 - Type:bugfix
 - ID:NA