diff --git a/duplocale-global-locale.patch b/duplocale-global-locale.patch
new file mode 100644
index 0000000..2f5b1df
--- /dev/null
+++ b/duplocale-global-locale.patch
@@ -0,0 +1,57 @@
+From 513331b788a3fa633f1d0417d43915e16a0c88f0 Mon Sep 17 00:00:00 2001
+From: Andreas Schwab <schwab@suse.de>
+Date: Wed, 6 Mar 2024 12:59:47 +0100
+Subject: [PATCH] duplocale: protect use of global locale (bug 23970)
+
+Protect the global locale from being modified while we compute the size of
+the locale category names.  That allows the use of the global locale in a
+single thread, while all other threads use the thread safe locale
+functions.
+---
+ locale/duplocale.c | 14 ++++++++------
+ 1 file changed, 8 insertions(+), 6 deletions(-)
+
+diff --git a/locale/duplocale.c b/locale/duplocale.c
+index a755ac5c36..bad476700f 100644
+--- a/locale/duplocale.c
++++ b/locale/duplocale.c
+@@ -43,6 +43,11 @@ __duplocale (locale_t dataset)
+   int cnt;
+   size_t names_len = 0;
+ 
++  /* If dataset points to _nl_global_locale, we need to prevent other
++     threads from modifying it.  We also modify global data below (the
++     usage counts).  */
++  __libc_rwlock_wrlock (__libc_setlocale_lock);
++
+   /* Calculate the total space we need to store all the names.  */
+   for (cnt = 0; cnt < __LC_LAST; ++cnt)
+     if (cnt != LC_ALL && dataset->__names[cnt] != _nl_C_name)
+@@ -55,9 +60,6 @@ __duplocale (locale_t dataset)
+     {
+       char *namep = (char *) (result + 1);
+ 
+-      /* We modify global data (the usage counts).  */
+-      __libc_rwlock_wrlock (__libc_setlocale_lock);
+-
+       for (cnt = 0; cnt < __LC_LAST; ++cnt)
+ 	if (cnt != LC_ALL)
+ 	  {
+@@ -78,11 +80,11 @@ __duplocale (locale_t dataset)
+       result->__ctype_b = dataset->__ctype_b;
+       result->__ctype_tolower = dataset->__ctype_tolower;
+       result->__ctype_toupper = dataset->__ctype_toupper;
+-
+-      /* It's done.  */
+-      __libc_rwlock_unlock (__libc_setlocale_lock);
+     }
+ 
++  /* It's done.  */
++  __libc_rwlock_unlock (__libc_setlocale_lock);
++
+   return result;
+ }
+ weak_alias (__duplocale, duplocale)
+-- 
+2.44.0
+
diff --git a/glibc.changes b/glibc.changes
index 37e2447..ba01efb 100644
--- a/glibc.changes
+++ b/glibc.changes
@@ -1,3 +1,9 @@
+-------------------------------------------------------------------
+Mon Mar 11 10:06:42 UTC 2024 - Andreas Schwab <schwab@suse.de>
+
+- duplocale-global-locale.patch: duplocale: protect use of global locale
+  (bsc#1220441, BZ #23970)
+
 -------------------------------------------------------------------
 Mon Feb 26 12:48:48 UTC 2024 - Andreas Schwab <schwab@suse.de>
 
diff --git a/glibc.spec b/glibc.spec
index 1afdcd9..d65bf94 100644
--- a/glibc.spec
+++ b/glibc.spec
@@ -341,6 +341,8 @@ Patch1021:      syslog-buffer-overflow.patch
 Patch1022:      qsort-invalid-cmp.patch
 # PATCH-FIX-UPSTREAM S390: Do not clobber r7 in clone (BZ #31402)
 Patch1023:      s390-clone-error-clobber-r7.patch
+# PATCH-FIX-UPSTREAM duplocale: protect use of global locale (BZ #23970)
+Patch1024:      duplocale-global-locale.patch
 
 ###
 # Patches awaiting upstream approval