1 files changed, 5 insertions, 1 deletions

diff --git a/lib/libc/stdlib/strtoull.c b/lib/libc/stdlib/strtoull.c
index 1720a8f6571c..0e80b0d51295 100644
--- a/lib/libc/stdlib/strtoull.c
+++ b/lib/libc/stdlib/strtoull.c
@@ -73,7 +73,11 @@ strtoull(const char * __restrict nptr, char ** __restrict endptr, int base)
 			c = *s++;
 	}
 	if ((base == 0 || base == 16) &&
-	    c == '0' && (*s == 'x' || *s == 'X')) {
+	    c == '0' && (*s == 'x' || *s == 'X') &&
+	    ((s[1] >= 'a' && s[1] <= 'f') ||
+	     (s[1] >= 'A' && s[1] <= 'F') ||
+	     (s[1] >= '0' && s[1] <= '9'))
+	   ) {
 		c = s[1];
 		s += 2;
 		base = 16;