1 files changed, 4 insertions, 0 deletions

diff --git a/src/lib/libcrypto/mem.c b/src/lib/libcrypto/mem.c
index 8f06d190a1..9ecb8d26b1 100644
--- a/src/lib/libcrypto/mem.c
+++ b/src/lib/libcrypto/mem.c
@@ -362,6 +362,10 @@ void *CRYPTO_realloc_clean(void *str, int old_len, int num, const char *file,
 
         if (num <= 0) return NULL;
 
+        /* We don't support shrinking the buffer. Note the memcpy that copies
+         * |old_len| bytes to the new buffer, below. */
+        if (num < old_len) return NULL;
+
         if (realloc_debug_func != NULL)
                 realloc_debug_func(str, NULL, num, file, line, 0);
         ret=malloc_ex_func(num,file,line);