diff --git a/lib/std/crypto.zig b/lib/std/crypto.zig
index 6f4ff863adbb8f8c46d4f3abd16f7dffd00c984c..d0ec3277e8b949871e2d96ce8977e8fb1539822f 100644
--- a/lib/std/crypto.zig
+++ b/lib/std/crypto.zig
@@ -57,3 +57,34 @@ test "crypto" {
     _ = @import("crypto/sha3.zig");
     _ = @import("crypto/x25519.zig");
 }
+
+test "issue #4532: no index out of bounds" {
+    const types = [_]type{
+        Md5,
+        Sha1,
+        Sha224,
+        Sha256,
+        Sha384,
+        Sha512,
+        Blake2s224,
+        Blake2s256,
+        Blake2b384,
+        Blake2b512,
+    };
+
+    inline for (types) |Hasher| {
+        var block = [_]u8{'#'} ** Hasher.block_length;
+        var out1: [Hasher.digest_length]u8 = undefined;
+        var out2: [Hasher.digest_length]u8 = undefined;
+
+        var h = Hasher.init();
+        h.update(block[0..]);
+        h.final(out1[0..]);
+        h.reset();
+        h.update(block[0..1]);
+        h.update(block[1..]);
+        h.final(out2[0..]);
+
+        std.testing.expectEqual(out1, out2);
+    }
+}
diff --git a/lib/std/crypto/blake2.zig b/lib/std/crypto/blake2.zig
index aa866acbe4b7d37486de1f5be78dab0f1072d9e9..e03d8f7dab877d9a46dc481055bdada2e35a3485 100644
--- a/lib/std/crypto/blake2.zig
+++ b/lib/std/crypto/blake2.zig
@@ -94,7 +94,7 @@ fn Blake2s(comptime out_len: usize) type {
             var off: usize = 0;
 
             // Partial buffer exists from previous update. Copy into buffer then hash.
-            if (d.buf_len != 0 and d.buf_len + b.len > 64) {
+            if (d.buf_len != 0 and d.buf_len + b.len >= 64) {
                 off += 64 - d.buf_len;
                 mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
                 d.t += 64;
@@ -331,7 +331,7 @@ fn Blake2b(comptime out_len: usize) type {
             var off: usize = 0;
 
             // Partial buffer exists from previous update. Copy into buffer then hash.
-            if (d.buf_len != 0 and d.buf_len + b.len > 128) {
+            if (d.buf_len != 0 and d.buf_len + b.len >= 128) {
                 off += 128 - d.buf_len;
                 mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
                 d.t += 128;
diff --git a/lib/std/crypto/md5.zig b/lib/std/crypto/md5.zig
index 41ce802dd7b116f71b87732cb4a9976990257ea2..d9dd08c9047df97f8c58ca723112133d74474126 100644
--- a/lib/std/crypto/md5.zig
+++ b/lib/std/crypto/md5.zig
@@ -63,7 +63,7 @@ pub const Md5 = struct {
         var off: usize = 0;
 
         // Partial buffer exists from previous update. Copy into buffer then hash.
-        if (d.buf_len != 0 and d.buf_len + b.len > 64) {
+        if (d.buf_len != 0 and d.buf_len + b.len >= 64) {
             off += 64 - d.buf_len;
             mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
 
diff --git a/lib/std/crypto/sha1.zig b/lib/std/crypto/sha1.zig
index b4d6e5c0cc70563f2dd8f2802e698b1d3123c32d..5be42180a16ec38826fb4a37a15df03264534f20 100644
--- a/lib/std/crypto/sha1.zig
+++ b/lib/std/crypto/sha1.zig
@@ -61,7 +61,7 @@ pub const Sha1 = struct {
         var off: usize = 0;
 
         // Partial buffer exists from previous update. Copy into buffer then hash.
-        if (d.buf_len != 0 and d.buf_len + b.len > 64) {
+        if (d.buf_len != 0 and d.buf_len + b.len >= 64) {
             off += 64 - d.buf_len;
             mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
 
diff --git a/lib/std/crypto/sha2.zig b/lib/std/crypto/sha2.zig
index 478cadd03c0e8765d3b5b641d441e59667a4e664..fd7ad532a3f7e3b224fa4dce39cb7dcc9342619a 100644
--- a/lib/std/crypto/sha2.zig
+++ b/lib/std/crypto/sha2.zig
@@ -116,7 +116,7 @@ fn Sha2_32(comptime params: Sha2Params32) type {
             var off: usize = 0;
 
             // Partial buffer exists from previous update. Copy into buffer then hash.
-            if (d.buf_len != 0 and d.buf_len + b.len > 64) {
+            if (d.buf_len != 0 and d.buf_len + b.len >= 64) {
                 off += 64 - d.buf_len;
                 mem.copy(u8, d.buf[d.buf_len..], b[0..off]);
 
@@ -458,7 +458,7 @@ fn Sha2_64(comptime params: Sha2Params64) type {
             var off: usize = 0;
 
             // Partial buffer exists from previous update. Copy into buffer then hash.
-            if (d.buf_len != 0 and d.buf_len + b.len > 128) {
+            if (d.buf_len != 0 and d.buf_len + b.len >= 128) {
                 off += 128 - d.buf_len;
                 mem.copy(u8, d.buf[d.buf_len..], b[0..off]);