From 7993203aa6bce6f3ca13a48c03caeab19f2fae5e Mon Sep 17 00:00:00 2001
From: Zhuyuyangyy <193758752+Zhuyuyangyy@users.noreply.github.com>
Date: Fri, 23 Oct 2026 17:34:52 +0800
Subject: [PATCH] Fix 63-character limit for simple hostname labels

---
 src/validators/hostname.py |  6 +++---
 tests/test_hostname.py     | 13 +++++++++++++
 tests/test_url.py          | 11 +++++++++++
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/src/validators/hostname.py b/src/validators/hostname.py
index e34ab7e4..c99a00f3 100644
--- a/src/validators/hostname.py
+++ b/src/validators/hostname.py
@@ -24,10 +24,10 @@ def _port_regex():
 @lru_cache
 def _simple_hostname_regex():
     """Simple hostname validation regex."""
-    # {0,59} because two characters are already matched at
-    # the beginning and at the end, making the range {1, 61}
+    # RFC 1035 limits each label to 63 octets. The first and last
+    # characters leave room for up to 61 characters in between.
     return re.compile(
-        r"^(?!-)[a-z0-9](?:[a-z0-9-]{0,59}[a-z0-9])?(?<!-)$", re.IGNORECASE | re.ASCII
+        r"^(?!-)[a-z0-9](?:[a-z0-9-]{0,61}[a-z0-9])?(?<!-)$", re.IGNORECASE | re.ASCII
     )
 
 
diff --git a/tests/test_hostname.py b/tests/test_hostname.py
index 83f00212..bee07e76 100644
--- a/tests/test_hostname.py
+++ b/tests/test_hostname.py
@@ -171,3 +171,16 @@ def test_returns_true_on_valid_top_level_domain_hostname(value: str):
 def test_returns_failed_validation_on_invalid_top_level_domain_hostname(value: str):
     """Test returns failed validation on hostname with a TLD not allowed by IANA."""
     assert isinstance(hostname(value, consider_tld=True), ValidationError)
+
+
+@pytest.mark.parametrize("length", [1, 61, 62, 63, 64])
+@pytest.mark.parametrize("port", ["", ":8080"])
+@pytest.mark.parametrize("rfc_1034", [False, True])
+def test_simple_hostname_label_length(length: int, port: str, rfc_1034: bool):
+    """Allow single labels up to 63 characters, with optional dots and ports."""
+    value = "a" * length + ("." if rfc_1034 else "") + port
+    result = hostname(value, rfc_1034=rfc_1034)
+    if length <= 63:
+        assert result is True
+    else:
+        assert isinstance(result, ValidationError)
diff --git a/tests/test_url.py b/tests/test_url.py
index d48a03ec..163dbf3a 100644
--- a/tests/test_url.py
+++ b/tests/test_url.py
@@ -299,3 +299,14 @@ def test_returns_true_on_valid_top_level_domain_url(value: str):
 def test_returns_failed_validation_on_invalid_top_level_domain_url(value: str):
     """Test returns failed validation on url with a TLD not allowed by IANA."""
     assert isinstance(url(value, consider_tld=True), ValidationError)
+
+
+@pytest.mark.parametrize("length", [61, 62, 63, 64])
+@pytest.mark.parametrize("port", ["", ":8080"])
+def test_url_simple_hostname_label_length(length: int, port: str):
+    """Apply the 63-character label limit to URLs allowing simple hosts."""
+    result = url("http://" + "a" * length + port + "/", simple_host=True)
+    if length <= 63:
+        assert result is True
+    else:
+        assert isinstance(result, ValidationError)