diff --git a/c/makeotf/makeotf_lib/source/hotconv/cmap.c b/c/makeotf/makeotf_lib/source/hotconv/cmap.c
index 2687c9104..0617ce705 100644
--- a/c/makeotf/makeotf_lib/source/hotconv/cmap.c
+++ b/c/makeotf/makeotf_lib/source/hotconv/cmap.c
@@ -291,7 +291,7 @@ static void CDECL cmapMsg(hotCtx g, int msgType, char *fmt, ...) {
     char msg[1024];
 
     va_start(ap, fmt);
-    vsprintf(msgVar, fmt, ap);
+    VSPRINTF_S(msgVar, sizeof(msgVar), fmt, ap);
     va_end(ap);
     sprintf(msg, "cmap{plat=%u,script=%u,lang=%u}: %s", h->platformId,
             h->scriptId, h->language, msgVar);
diff --git a/c/makeotf/makeotf_lib/source/hotconv/feat.c b/c/makeotf/makeotf_lib/source/hotconv/feat.c
index d6bb61bbe..ba5ccacf9 100644
--- a/c/makeotf/makeotf_lib/source/hotconv/feat.c
+++ b/c/makeotf/makeotf_lib/source/hotconv/feat.c
@@ -445,7 +445,7 @@ static void CDECL zzerrVA(char *fmt, ...) {
     char msg[1024];
 
     va_start(ap, fmt);
-    vsprintf(msg, fmt, ap);
+    VSPRINTF_S(msg, sizeof(msg), fmt, ap);
     va_end(ap);
     zzerr(msg);
 }
@@ -458,7 +458,7 @@ static void CDECL featMsg(int msgType, char *fmt, ...) {
     char msg[1024];
 
     va_start(ap, fmt);
-    vsprintf(msgVar, fmt, ap);
+    VSPRINTF_S(msgVar, sizeof(msgVar), fmt, ap);
     va_end(ap);
     sprintf(msg, "%s [%s %d]", msgVar, INCL.file, zzline);
 
diff --git a/c/makeotf/makeotf_lib/source/hotconv/hot.c b/c/makeotf/makeotf_lib/source/hotconv/hot.c
index 9380a579a..8b4e0239f 100644
--- a/c/makeotf/makeotf_lib/source/hotconv/hot.c
+++ b/c/makeotf/makeotf_lib/source/hotconv/hot.c
@@ -1851,9 +1851,13 @@ void CDECL hotMsg(hotCtx g, int level, char *fmt, ...) {
 #define MAX_NOTE_LEN 1024
             char message[MAX_NOTE_LEN + 1024];
             char *p;
+            size_t p_size;
+
+            p_size = sizeof(message);
             if ((g->font.FontName.cnt != 0) && (lenName < MAX_NOTE_LEN)) {
                 sprintf(message, "<%s> ", g->font.FontName.array);
                 p = &message[lenName];
+                p_size -= lenName;
             } else {
                 p = message;
             }
@@ -1867,7 +1871,7 @@ void CDECL hotMsg(hotCtx g, int level, char *fmt, ...) {
             }
 
             va_start(ap, fmt);
-            vsprintf(p, fmt, ap);
+            VSPRINTF_S(p, p_size, fmt, ap);
             va_end(ap);
             g->cb.message(g->cb.ctx, level, message);
         }
diff --git a/c/makeotf/makeotf_lib/source/hotconv/map.c b/c/makeotf/makeotf_lib/source/hotconv/map.c
index c739b63be..13335f936 100644
--- a/c/makeotf/makeotf_lib/source/hotconv/map.c
+++ b/c/makeotf/makeotf_lib/source/hotconv/map.c
@@ -674,7 +674,7 @@ static void CDECL CMapMsg(mapCtx h, int msgType, char *fmt, ...) {
     char msg[2048];
 
     va_start(ap, fmt);
-    vsprintf(msgVar, fmt, ap);
+    VSPRINTF_S(msgVar, sizeof(msgVar), fmt, ap);
     va_end(ap);
     sprintf(msg, "%s [%s]", msgVar, h->ps.cb.psId ? h->ps.cb.psId(h->ps.cb.ctx) : "");
 
diff --git a/c/makeotf/makeotf_lib/source/pstoken/pstoken.c b/c/makeotf/makeotf_lib/source/pstoken/pstoken.c
index e9b493ce9..2fefe6f14 100644
--- a/c/makeotf/makeotf_lib/source/pstoken/pstoken.c
+++ b/c/makeotf/makeotf_lib/source/pstoken/pstoken.c
@@ -794,7 +794,7 @@ void CDECL psWarning(psCtx h, char *fmt, ...) {
 
         /* Format message */
         va_start(ap, fmt);
-        vsprintf(text, fmt, ap);
+        VSPRINTF_S(text, sizeof(text), fmt, ap);
 
         if (h->cb.psId != NULL) {
             /* Append source data id */
@@ -816,7 +816,7 @@ void CDECL psFatal(psCtx h, char *fmt, ...) {
         char text[513];
 
         va_start(ap, fmt);
-        vsprintf(text, fmt, ap);
+        VSPRINTF_S(text, sizeof(text), fmt, ap);
 
         if (h->cb.psId != NULL) {
             /* Append source data id */
diff --git a/c/makeotf/makeotf_lib/source/typecomp/parse.c b/c/makeotf/makeotf_lib/source/typecomp/parse.c
index d6e30c2f6..a61b10fee 100644
--- a/c/makeotf/makeotf_lib/source/typecomp/parse.c
+++ b/c/makeotf/makeotf_lib/source/typecomp/parse.c
@@ -388,7 +388,7 @@ void CDECL parseWarning(tcCtx g, char *fmt, ...) {
 
         /* Format and report message */
         va_start(ap, fmt);
-        vsprintf(text, fmt, ap);
+        VSPRINTF_S(text, sizeof(text), fmt, ap);
         g->cb.message(g->cb.ctx, tcWARNING, text);
         va_end(ap);
     }
@@ -404,7 +404,7 @@ void CDECL parseNewGlyphReport(tcCtx g, char *fmt, ...) {
 
         /* Format and report message */
         va_start(ap, fmt);
-        vsprintf(text, fmt, ap);
+        VSPRINTF_S(text, sizeof(text), fmt, ap);
         g->cb.message(g->cb.ctx, tcNOTE, text);
         va_end(ap);
     }
@@ -423,7 +423,7 @@ void CDECL parseFatal(tcCtx g, char *fmt, ...) {
 
         /* Format and report message */
         va_start(ap, fmt);
-        vsprintf(text, fmt, ap);
+        VSPRINTF_S(text, sizeof(text), fmt, ap);
         g->cb.message(ctx, tcFATAL, text);
         va_end(ap);
     }
diff --git a/c/makeotf/makeotf_lib/source/typecomp/tc.c b/c/makeotf/makeotf_lib/source/typecomp/tc.c
index 2924116ea..adc305007 100644
--- a/c/makeotf/makeotf_lib/source/typecomp/tc.c
+++ b/c/makeotf/makeotf_lib/source/typecomp/tc.c
@@ -1060,7 +1060,7 @@ void CDECL tcFatal(tcCtx g, char *fmt, ...) {
         va_list ap;
 
         va_start(ap, fmt);
-        vsprintf(text, fmt, ap);
+        VSPRINTF_S(text, sizeof(text), fmt, ap);
 
         if (g->cb.psId != NULL) {
             /* Append source data id */
@@ -1081,7 +1081,7 @@ void CDECL tcWarning(tcCtx g, char *fmt, ...) {
         va_list ap;
 
         va_start(ap, fmt);
-        vsprintf(text, fmt, ap);
+        VSPRINTF_S(text, sizeof(text), fmt, ap);
 
         if (g->cb.psId != NULL) {
             /* Append source data id */
@@ -1101,7 +1101,7 @@ void CDECL tcNote(tcCtx g, char *fmt, ...) {
         va_list ap;
 
         va_start(ap, fmt);
-        vsprintf(text, fmt, ap);
+        VSPRINTF_S(text, sizeof(text), fmt, ap);
 
         if (g->cb.psId != NULL) {
             /* Append source data id */
diff --git a/c/makeotf/source/cbpriv.c b/c/makeotf/source/cbpriv.c
index 0eacf601f..2940d3009 100644
--- a/c/makeotf/source/cbpriv.c
+++ b/c/makeotf/source/cbpriv.c
@@ -18,7 +18,7 @@ void cbFatal(cbCtx h, char *fmt, ...) {
     char text[512];
     va_list ap;
     va_start(ap, fmt);
-    vsnprintf(text, sizeof(text), fmt, ap);
+    VSPRINTF_S(text, sizeof(text), fmt, ap);
     message(h, hotFATAL, text);
     va_end(ap);
     if (!KeepGoing) {
@@ -31,7 +31,7 @@ void cbWarning(cbCtx h, char *fmt, ...) {
     char text[512];
     va_list ap;
     va_start(ap, fmt);
-    vsnprintf(text, sizeof(text), fmt, ap);
+    VSPRINTF_S(text, sizeof(text), fmt, ap);
     message(h, hotWARNING, text);
     va_end(ap);
 }
diff --git a/c/public/lib/api/ctlshare.h b/c/public/lib/api/ctlshare.h
index c3e76d7d7..22dd6675b 100644
--- a/c/public/lib/api/ctlshare.h
+++ b/c/public/lib/api/ctlshare.h
@@ -537,7 +537,7 @@ enum {
 #define SPRINTF_S(b, l, f, ...) sprintf(b, f, ##__VA_ARGS__)
 #endif
 #ifndef VSPRINTF_S
-#define VSPRINTF_S(b, l, f, ...) vsprintf(b, f, ##__VA_ARGS__)
+#define VSPRINTF_S vsnprintf
 #endif
 #ifndef SSCANF_S
 #define SSCANF_S sscanf
diff --git a/c/public/lib/source/cffwrite/cffwrite.c b/c/public/lib/source/cffwrite/cffwrite.c
index 77c6ca87f..2dd4b4b80 100644
--- a/c/public/lib/source/cffwrite/cffwrite.c
+++ b/c/public/lib/source/cffwrite/cffwrite.c
@@ -2281,12 +2281,11 @@ void cfwFree(cfwCtx g) {
 /* Write message to debug stream from va_list. */
 static void vmessage(cfwCtx g, char *fmt, va_list ap) {
     char text[500];
-    const size_t textLen = sizeof(text);
 
     if (g->stm.dbg == NULL) {
         return; /* Debug stream not available */
     }
-    VSPRINTF_S(text, textLen, fmt, ap);
+    VSPRINTF_S(text, sizeof(text), fmt, ap);
     (void)g->cb.stm.write(&g->cb.stm, g->stm.dbg, strlen(text), text);
 }
 
diff --git a/c/public/lib/source/pdfwrite/pdfwrite.c b/c/public/lib/source/pdfwrite/pdfwrite.c
index 22dcf9b70..c6d79e04e 100644
--- a/c/public/lib/source/pdfwrite/pdfwrite.c
+++ b/c/public/lib/source/pdfwrite/pdfwrite.c
@@ -504,7 +504,7 @@ static void CTL_CDECL dstPrint(pdwCtx h, char *fmt, ...) {
     char buf[500];
     va_list ap;
     va_start(ap, fmt);
-    vsprintf(buf, fmt, ap);
+    VSPRINTF_S(buf, sizeof(buf), fmt, ap);
     dstWrite(h, strlen(buf), buf);
     va_end(ap);
 }
@@ -541,7 +541,7 @@ static void CTL_CDECL stmPrint(pdwCtx h, long iStm, char *fmt, ...) {
     long length;
     va_list ap;
     va_start(ap, fmt);
-    vsprintf(buf, fmt, ap);
+    VSPRINTF_S(buf, sizeof(buf), fmt, ap);
     va_end(ap);
     length = (long)strlen(buf);
     memcpy(dnaEXTEND(h->stms[iStm], length), buf, length);
@@ -617,7 +617,7 @@ static void CTL_CDECL textShow(pdwCtx h, char *fmt, ...) {
 
     /* Format text */
     va_start(ap, fmt);
-    vsprintf(src, fmt, ap);
+    VSPRINTF_S(src, sizeof(src), fmt, ap);
     va_end(ap);
 
     /* Double backslashes */
diff --git a/c/public/lib/source/svgwrite/svgwrite.c b/c/public/lib/source/svgwrite/svgwrite.c
index 2e67958a7..39e00b674 100644
--- a/c/public/lib/source/svgwrite/svgwrite.c
+++ b/c/public/lib/source/svgwrite/svgwrite.c
@@ -265,7 +265,7 @@ static void CTL_CDECL writeFmt(svwCtx h, char *fmt, ...) {
     char buf[200];
     va_list ap;
     va_start(ap, fmt);
-    vsprintf(buf, fmt, ap);
+    VSPRINTF_S(buf, sizeof(buf), fmt, ap);
     writeStr(h, buf);
     va_end(ap);
 }
diff --git a/c/public/lib/source/svread/svread.c b/c/public/lib/source/svread/svread.c
index 217f5653b..b45b42a13 100644
--- a/c/public/lib/source/svread/svread.c
+++ b/c/public/lib/source/svread/svread.c
@@ -167,7 +167,7 @@ static void vmessage(svrCtx h, char *fmt, va_list ap) {
     if (h->stm.dbg == NULL)
         return; /* Debug stream not available */
 
-    vsnprintf(text, BUFSIZ, fmt, ap);
+    VSPRINTF_S(text, BUFSIZ, fmt, ap);
     (void)h->cb.stm.write(&h->cb.stm, h->stm.dbg, strlen(text), text);
 }
 
diff --git a/c/public/lib/source/t1read/t1read.c b/c/public/lib/source/t1read/t1read.c
index 8e7d7b690..778803762 100644
--- a/c/public/lib/source/t1read/t1read.c
+++ b/c/public/lib/source/t1read/t1read.c
@@ -201,7 +201,7 @@ static void vmessage(t1rCtx h, char *fmt, va_list ap) {
     if (h->stm.dbg == NULL)
         return; /* Debug stream not available */
 
-    vsnprintf(text, 500, fmt, ap);
+    VSPRINTF_S(text, 500, fmt, ap);
     (void)h->cb.stm.write(&h->cb.stm, h->stm.dbg, strlen(text), text);
 }
 
diff --git a/c/public/lib/source/t1write/t1write.c b/c/public/lib/source/t1write/t1write.c
index f81b2b1ae..e16387408 100644
--- a/c/public/lib/source/t1write/t1write.c
+++ b/c/public/lib/source/t1write/t1write.c
@@ -306,7 +306,7 @@ static void CTL_CDECL writeFmt(t1wCtx h, char *fmt, ...) {
     char buf[200];
     va_list ap;
     va_start(ap, fmt);
-    vsprintf(buf, fmt, ap);
+    VSPRINTF_S(buf, sizeof(buf), fmt, ap);
     writeStr(h, buf);
     va_end(ap);
 }
diff --git a/c/public/lib/source/ttread/ttread.c b/c/public/lib/source/ttread/ttread.c
index 03c69b410..965e40d2d 100644
--- a/c/public/lib/source/ttread/ttread.c
+++ b/c/public/lib/source/ttread/ttread.c
@@ -457,7 +457,7 @@ static void vmessage(ttrCtx h, char *fmt, va_list ap) {
     if (h->stm.dbg == NULL)
         return; /* Debug stream not available */
 
-    vsprintf(text, fmt, ap);
+    VSPRINTF_S(text, sizeof(text), fmt, ap);
     (void)h->cb.stm.write(&h->cb.stm, h->stm.dbg, strlen(text), text);
 }
 
diff --git a/c/public/lib/source/uforead/uforead.c b/c/public/lib/source/uforead/uforead.c
index 52b91b0d6..ed0c90335 100644
--- a/c/public/lib/source/uforead/uforead.c
+++ b/c/public/lib/source/uforead/uforead.c
@@ -300,7 +300,7 @@ static void vmessage(ufoCtx h, char* fmt, va_list ap) {
     if (h->stm.dbg == NULL)
         return; /* Debug stream not available */
 
-    vsprintf(text, fmt, ap);
+    VSPRINTF_S(text, sizeof(text), fmt, ap);
     (void)h->cb.stm.write(&h->cb.stm, h->stm.dbg, strlen(text), text);
 }