diff --git a/include/ssp/string.h b/include/ssp/string.h
--- a/include/ssp/string.h
+++ b/include/ssp/string.h
@@ -109,6 +109,8 @@
 __ssp_bos_icheck3_restrict(mempcpy, void *, const void *)
 __ssp_bos_icheck3(memmove, void *, const void *)
 __ssp_bos_icheck3(memset, void *, int)
+__ssp_redirect(void *, memset_explicit, (void *__buf, int __ch, size_t __len),
+    (__buf, __ch, __len));
 __ssp_bos_icheck2_restrict(stpcpy, char *, const char *)
 __ssp_bos_icheck3_restrict(stpncpy, char *, const char *)
 __ssp_bos_icheck2_restrict(strcpy, char *, const char *)
diff --git a/include/string.h b/include/string.h
--- a/include/string.h
+++ b/include/string.h
@@ -71,6 +71,9 @@
 void	*(mempcpy)(void * __restrict, const void * __restrict, size_t);
 #endif
 void	*(memset)(void *, int, size_t);
+#if __BSD_VISIBLE
+void	*memset_explicit(void *, int, size_t);
+#endif
 #if __POSIX_VISIBLE >= 200809
 char	*(stpcpy)(char * __restrict, const char * __restrict);
 char	*(stpncpy)(char * __restrict, const char * __restrict, size_t);
diff --git a/lib/libc/string/Makefile.inc b/lib/libc/string/Makefile.inc
--- a/lib/libc/string/Makefile.inc
+++ b/lib/libc/string/Makefile.inc
@@ -11,6 +11,7 @@
 	ffs.c ffsl.c ffsll.c fls.c flsl.c flsll.c \
 	memccpy.c memchr.c memrchr.c memcmp.c \
 	memcpy.c memmem.c memmove.c mempcpy.c memset.c memset_s.c \
+	memset_explicit.c \
 	stpcpy.c stpncpy.c strcasecmp.c \
 	strcat.c strcasestr.c strchr.c strchrnul.c strcmp.c strcoll.c strcpy.c\
 	strcspn.c strdup.c strerror.c strlcat.c strlcpy.c strlen.c strmode.c \
@@ -62,7 +63,8 @@
 MLINKS+=index.3 rindex.3
 MLINKS+=memchr.3 memrchr.3
 MLINKS+=memcpy.3 mempcpy.3
-MLINKS+=memset.3 memset_s.3
+MLINKS+=memset.3 memset_s.3 \
+	memset.3 memset_explicit.3
 MLINKS+=strcasecmp.3 strncasecmp.3 \
 	strcasecmp.3 strcasecmp_l.3 \
 	strcasecmp.3 strncasecmp_l.3
diff --git a/lib/libc/string/Symbol.map b/lib/libc/string/Symbol.map
--- a/lib/libc/string/Symbol.map
+++ b/lib/libc/string/Symbol.map
@@ -116,6 +116,10 @@
 	wmempcpy;
 };
 
+FBSD_1.8 {
+	memset_explicit;
+};
+
 FBSDprivate_1.0 {
 	__strtok_r;
 };
diff --git a/lib/libc/string/memset.3 b/lib/libc/string/memset.3
--- a/lib/libc/string/memset.3
+++ b/lib/libc/string/memset.3
@@ -29,7 +29,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd August 19, 2018
+.Dd October 24, 2024
 .Dt MEMSET 3
 .Os
 .Sh NAME
@@ -41,6 +41,8 @@
 .In string.h
 .Ft void *
 .Fn memset "void *dest" "int c" "size_t len"
+.Ft void *
+.Fn memset_explicit "void *dest" "int c" "size_t len"
 .Fd #define __STDC_WANT_LIB_EXT1__ 1
 .Ft errno_t
 .Fn memset_s "void *dest" "rsize_t destsz" "int c" "rsize_t len"
@@ -68,6 +70,13 @@
 is an invalid pointer.
 .Pp
 The
+.Fn memset_explicit
+function behaves the same as
+.Fn memset, but will not be removed by a compiler's dead store
+optimization pass, making it useful for clearing sensitive memory
+such as a password.
+.Pp
+The
 .Fn memset_s
 function behaves the same as
 .Fn memset
@@ -108,7 +117,9 @@
 .Sh RETURN VALUES
 The
 .Fn memset
-function returns its first argument.
+and
+.Fn memset_explicit
+functions return their first argument.
 The
 .Fn memset_s
 function returns zero on success, non-zero on error.
@@ -128,3 +139,6 @@
 conforms to
 .St -isoC-2011
 K.3.7.4.1.
+.Fn memset_explicit
+conforms to
+.St -isoC-2024 .
diff --git a/lib/libc/string/memset_explicit.c b/lib/libc/string/memset_explicit.c
new file mode 100644
--- /dev/null
+++ b/lib/libc/string/memset_explicit.c
@@ -0,0 +1,27 @@
+/*-
+ * SPDF-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2024 Robert Clausecker <fuz@FreeBSD.org>
+ */
+
+#include <string.h>
+#include <ssp/ssp.h>
+
+__attribute__((weak)) void __memset_explicit_hook(void *, int, size_t);
+
+__attribute__((weak)) void
+__memset_explicit_hook(void *buf, int ch, size_t len)
+{
+	(void)buf;
+	(void)ch;
+	(void)len;
+}
+
+void *
+__ssp_real(memset_explicit)(void *buf, int ch, size_t len)
+{
+	memset(buf, ch, len);
+	__memset_explicit_hook(buf, ch, len);
+
+	return (buf);
+}
diff --git a/lib/libc/tests/secure/fortify_string_test.c b/lib/libc/tests/secure/fortify_string_test.c
--- a/lib/libc/tests/secure/fortify_string_test.c
+++ b/lib/libc/tests/secure/fortify_string_test.c
@@ -685,6 +685,133 @@
 
 }
 
+ATF_TC_WITHOUT_HEAD(memset_explicit_before_end);
+ATF_TC_BODY(memset_explicit_before_end, tc)
+{
+#define BUF &__stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char __buf[42];
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(__stack.__buf);
+	const size_t __len = 42 - 1;
+	const size_t __idx __unused = __len - 1;
+
+	memset_explicit(__stack.__buf, 0, __len);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(memset_explicit_end);
+ATF_TC_BODY(memset_explicit_end, tc)
+{
+#define BUF &__stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char __buf[42];
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(__stack.__buf);
+	const size_t __len = 42;
+	const size_t __idx __unused = __len - 1;
+
+	memset_explicit(__stack.__buf, 0, __len);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(memset_explicit_heap_before_end);
+ATF_TC_BODY(memset_explicit_heap_before_end, tc)
+{
+#define BUF __stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char * __buf;
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(*__stack.__buf) * (42);
+	const size_t __len = 42 - 1;
+	const size_t __idx __unused = __len - 1;
+
+	__stack.__buf = malloc(__bufsz);
+
+	memset_explicit(__stack.__buf, 0, __len);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(memset_explicit_heap_end);
+ATF_TC_BODY(memset_explicit_heap_end, tc)
+{
+#define BUF __stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char * __buf;
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(*__stack.__buf) * (42);
+	const size_t __len = 42;
+	const size_t __idx __unused = __len - 1;
+
+	__stack.__buf = malloc(__bufsz);
+
+	memset_explicit(__stack.__buf, 0, __len);
+#undef BUF
+
+}
+
+ATF_TC_WITHOUT_HEAD(memset_explicit_heap_after_end);
+ATF_TC_BODY(memset_explicit_heap_after_end, tc)
+{
+#define BUF __stack.__buf
+	struct {
+		uint8_t padding_l;
+		unsigned char * __buf;
+		uint8_t padding_r;
+	} __stack;
+	const size_t __bufsz __unused = sizeof(*__stack.__buf) * (42);
+	const size_t __len = 42 + 1;
+	const size_t __idx __unused = __len - 1;
+	pid_t __child;
+	int __status;
+
+	__child = fork();
+	ATF_REQUIRE(__child >= 0);
+	if (__child > 0)
+		goto monitor;
+
+	/* Child */
+	disable_coredumps();
+	__stack.__buf = malloc(__bufsz);
+
+	memset_explicit(__stack.__buf, 0, __len);
+	_exit(EX_SOFTWARE);	/* Should have aborted. */
+
+monitor:
+	while (waitpid(__child, &__status, 0) != __child) {
+		ATF_REQUIRE_EQ(EINTR, errno);
+	}
+
+	if (!WIFSIGNALED(__status)) {
+		switch (WEXITSTATUS(__status)) {
+		case EX_SOFTWARE:
+			atf_tc_fail("FORTIFY_SOURCE failed to abort");
+			break;
+		case EX_OSERR:
+			atf_tc_fail("setrlimit(2) failed");
+			break;
+		default:
+			atf_tc_fail("child exited with status %d",
+			    WEXITSTATUS(__status));
+		}
+	} else {
+		ATF_REQUIRE_EQ(SIGABRT, WTERMSIG(__status));
+	}
+#undef BUF
+
+}
+
 ATF_TC_WITHOUT_HEAD(stpcpy_before_end);
 ATF_TC_BODY(stpcpy_before_end, tc)
 {
@@ -1899,6 +2026,11 @@
 	ATF_TP_ADD_TC(tp, memset_heap_before_end);
 	ATF_TP_ADD_TC(tp, memset_heap_end);
 	ATF_TP_ADD_TC(tp, memset_heap_after_end);
+	ATF_TP_ADD_TC(tp, memset_explicit_before_end);
+	ATF_TP_ADD_TC(tp, memset_explicit_end);
+	ATF_TP_ADD_TC(tp, memset_explicit_heap_before_end);
+	ATF_TP_ADD_TC(tp, memset_explicit_heap_end);
+	ATF_TP_ADD_TC(tp, memset_explicit_heap_after_end);
 	ATF_TP_ADD_TC(tp, stpcpy_before_end);
 	ATF_TP_ADD_TC(tp, stpcpy_end);
 	ATF_TP_ADD_TC(tp, stpcpy_heap_before_end);
diff --git a/lib/libc/tests/secure/generate-fortify-tests.lua b/lib/libc/tests/secure/generate-fortify-tests.lua
--- a/lib/libc/tests/secure/generate-fortify-tests.lua
+++ b/lib/libc/tests/secure/generate-fortify-tests.lua
@@ -630,6 +630,15 @@
 			},
 			exclude = excludes_stack_overflow,
 		},
+		{
+			func = "memset_explicit",
+			arguments = {
+				"__buf",
+				"0",
+				"__len",
+			},
+			exclude = excludes_stack_overflow,
+		},
 		{
 			func = "stpcpy",
 			arguments = {