diff --git a/Lib/http/cookiejar.py b/Lib/http/cookiejar.py
index 68cf16c93cc1c8..7345cba5a94e51 100644
--- a/Lib/http/cookiejar.py
+++ b/Lib/http/cookiejar.py
@@ -656,16 +656,15 @@ def request_path(request):
     return path
 
 def request_port(request):
-    host = request.host
-    i = host.find(':')
-    if i >= 0:
-        port = host[i+1:]
-        try:
-            int(port)
-        except ValueError:
-            _debug("nonnumeric port: '%s'", port)
-            return None
+    match = cut_port_re.search(request.host)
+    if match:
+        port = match[0].removeprefix(':')
     else:
+        i = request.host.rfind(':')
+        if (i >= 0
+            and not ']' in request.host[i+1:]
+            and not request.host.startswith('[')): # to prevent IPv6 addresses
+                _debug("nonnumeric port: '%s'", request.host[i+1:])
         port = DEFAULT_HTTP_PORT
     return port
 
@@ -1075,11 +1074,7 @@ def set_ok_domain(self, cookie, request):
 
     def set_ok_port(self, cookie, request):
         if cookie.port_specified:
-            req_port = request_port(request)
-            if req_port is None:
-                req_port = "80"
-            else:
-                req_port = str(req_port)
+            req_port = str(request_port(request))
             for p in cookie.port.split(","):
                 try:
                     int(p)
@@ -1148,8 +1143,6 @@ def return_ok_expires(self, cookie, request):
     def return_ok_port(self, cookie, request):
         if cookie.port:
             req_port = request_port(request)
-            if req_port is None:
-                req_port = "80"
             for p in cookie.port.split(","):
                 if p == req_port:
                     break
diff --git a/Lib/test/test_http_cookiejar.py b/Lib/test/test_http_cookiejar.py
index 04cb440cd4ccf6..1970b993d6acdf 100644
--- a/Lib/test/test_http_cookiejar.py
+++ b/Lib/test/test_http_cookiejar.py
@@ -839,6 +839,19 @@ def test_request_port(self):
         req = urllib.request.Request("http://www.acme.com/",
                                      headers={"Host": "www.acme.com:4321"})
         self.assertEqual(request_port(req), DEFAULT_HTTP_PORT)
+        req = urllib.request.Request("http://www.acme.com:",
+                                     headers={"Host": "www.acme.com:4321"})
+        self.assertEqual(request_port(req), DEFAULT_HTTP_PORT)
+        req = urllib.request.Request("http://www.acme.com:not_a_port",
+                                     headers={"Host": "www.acme.com:4321"})
+        self.assertEqual(request_port(req), DEFAULT_HTTP_PORT)
+        req = urllib.request.Request("http://[::1]:1234",
+                                     headers={"Host": "[::1]:4321"})
+        self.assertEqual(request_port(req), "1234")
+        req = urllib.request.Request("http://[::1]",
+                                     headers={"Host": "[::1]:4321"})
+        self.assertEqual(request_port(req), DEFAULT_HTTP_PORT)
+
 
     def test_request_host(self):
         # this request is illegal (RFC2616, 14.2.3)
@@ -1262,6 +1275,72 @@ def test_missing_final_slash(self):
         c.add_cookie_header(req)
         self.assertTrue(req.has_header("Cookie"))
 
+    def test_set_ok_port(self):
+        pol = DefaultCookiePolicy()
+        c = CookieJar(policy=pol)
+        headers_with_port_1234 = ["Set-Cookie: CUSTOMER=WILE_E_COYOTE; path=/; port=1234"]
+        headers_with_default_port = ["Set-Cookie: CUSTOMER=WILE_E_COYOTE; path=/; port=80"]
+        req = urllib.request.Request("http://127.0.0.1:1234")
+        res = FakeResponse(headers_with_port_1234, "http://127.0.0.1:1234")
+        self.assertTrue(pol.set_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://acme.com:1234")
+        res = FakeResponse(headers_with_port_1234, "http://acme.com:1234")
+        self.assertTrue(pol.set_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://[::1]:1234")
+        res = FakeResponse(headers_with_port_1234, "http://[::1]:1234")
+        self.assertTrue(pol.set_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://[::1]:1235")
+        res = FakeResponse(headers_with_port_1234, "http://[::1]:1235")
+        self.assertFalse(pol.set_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://acme.com:")
+        res = FakeResponse(headers_with_default_port, "http://acme.com:")
+        self.assertTrue(pol.set_ok_port(c.make_cookies(res, req)[0], req))
+        res = FakeResponse(headers_with_port_1234, "http://acme.com:")
+        self.assertFalse(pol.set_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://acme.com:not_a_port")
+        res = FakeResponse(headers_with_default_port, "http://acme.com:not_a_port")
+        self.assertTrue(pol.set_ok_port(c.make_cookies(res, req)[0], req))
+        res = FakeResponse(headers_with_port_1234, "http://acme.com:not_a_port")
+        self.assertFalse(pol.set_ok_port(c.make_cookies(res, req)[0], req))
+
+    def test_return_ok_port(self):
+        pol = DefaultCookiePolicy()
+        c = CookieJar(policy=pol)
+        headers_with_port_1234 = ["Set-Cookie: CUSTOMER=WILE_E_COYOTE; path=/; port=1234"]
+        headers_with_default_port = ["Set-Cookie: CUSTOMER=WILE_E_COYOTE; path=/; port=80"]
+        req = urllib.request.Request("http://127.0.0.1:1234")
+        res = FakeResponse(headers_with_port_1234, "http://127.0.0.1:1234")
+        self.assertTrue(pol.return_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://acme.com:1234")
+        res = FakeResponse(headers_with_port_1234, "http://acme.com:1234")
+        self.assertTrue(pol.return_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://[::1]:1234")
+        res = FakeResponse(headers_with_port_1234, "http://[::1]:1234")
+        self.assertTrue(pol.return_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://[::1]:1235")
+        res = FakeResponse(headers_with_port_1234, "http://[::1]:1235")
+        self.assertFalse(pol.return_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://acme.com:")
+        res = FakeResponse(headers_with_default_port, "http://acme.com:")
+        self.assertTrue(pol.return_ok_port(c.make_cookies(res, req)[0], req))
+        res = FakeResponse(headers_with_port_1234, "http://acme.com:")
+        self.assertFalse(pol.return_ok_port(c.make_cookies(res, req)[0], req))
+
+        req = urllib.request.Request("http://acme.com:not_a_port")
+        res = FakeResponse(headers_with_default_port, "http://acme.com:not_a_port")
+        self.assertTrue(pol.return_ok_port(c.make_cookies(res, req)[0], req))
+        res = FakeResponse(headers_with_port_1234, "http://acme.com:not_a_port")
+        self.assertFalse(pol.return_ok_port(c.make_cookies(res, req)[0], req))
+
     def test_domain_mirror(self):
         pol = DefaultCookiePolicy(rfc2965=True)
 
diff --git a/Misc/NEWS.d/next/Library/2025-06-28-14-10-07.gh-issue-135993.Gmyux9.rst b/Misc/NEWS.d/next/Library/2025-06-28-14-10-07.gh-issue-135993.Gmyux9.rst
new file mode 100644
index 00000000000000..f2113ec786be1e
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-06-28-14-10-07.gh-issue-135993.Gmyux9.rst
@@ -0,0 +1,2 @@
+:mod:`http.cookiejar`: Fix a bug that occurs when :class:`~http.cookiejar.DefaultCookiePolicy`
+attempts to parse the port of an IPv6 address in func ``request_port()``. Patch by Weilin Du.