diff --git a/backport-CVE-2021-27135.patch b/backport-CVE-2021-27135.patch
new file mode 100644
index 0000000..811d559
--- /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
+@@ -4323,6 +4323,7 @@ SaltTextAway(XtermWidget xw,
+     int i;
+     int eol;
+     int need = 0;
++    size_t have = 0;
+     Char *line;
+     Char *lp;
+     CELL first = *cellc;
+@@ -4357,7 +4358,11 @@ SaltTextAway(XtermWidget xw,
+ 
+     /* UTF-8 may require more space */
+     if_OPT_WIDE_CHARS(screen, {
+-	need *= 4;
++	if (need > 0) {
++	    if (screen->max_combining > 0)
++		need += screen->max_combining;
++	    need *= 6;
++	}
+     });
+ 
+     /* now get some memory to save it in */
+@@ -4395,10 +4400,20 @@ SaltTextAway(XtermWidget xw,
+     }
+     *lp = '\0';			/* make sure we have end marked */
+ 
+-    TRACE(("Salted TEXT:%u:%s\n", (unsigned) (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) need) {
++	scp->data_limit = have + 1;
++	line = realloc(line, scp->data_limit);
++    }
++
++    TRACE(("Salted TEXT:%u:%s\n", (unsigned) have,
++	   visibleChars(line, (unsigned) have)));
+ 
+-    scp->data_length = (size_t) (lp - line);
++    scp->data_length = have;
+ }
+ 
+ #if OPT_PASTE64
diff --git a/xterm.spec b/xterm.spec
index 3f2dc64..7c638b7 100644
--- a/xterm.spec
+++ b/xterm.spec
@@ -1,11 +1,13 @@
 Name:		xterm
 Version:	363
-Release:        1
+Release:        2
 Summary:	It is a terminal emulator for the X Window System
 License:	MIT
 URL:		http://invisible-island.net/xterm
 Source0:	https://invisible-mirror.net/archives/xterm/xterm-%{version}.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> - 363-2
+- fix CVE-2021-27135
+
 * Thu Jan 28 2021 jinzhimin <jinzhimin2@huawei.com> - 363-1
 - Upgrade to 363