diff --git a/pyproject.toml b/pyproject.toml
index d177b56..83aecce 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -120,7 +120,7 @@ dev = [
     # across the six advisories that affected the old >=2.3.8 floor
     # (CVE-2024-34069, CVE-2024-49766, CVE-2024-49767, CVE-2025-66221,
     # CVE-2026-21860, CVE-2026-27199).
-    "werkzeug==3.1.8",
+    "werkzeug==3.1.9",
 ]
 # The SDK supports both pydantic majors (permit/utils/pydantic_version.py), and
 # CI runs the suite once per major. Each lane is a group so both resolutions
diff --git a/uv.lock b/uv.lock
index 5c853a5..2f6e340 100644
--- a/uv.lock
+++ b/uv.lock
@@ -1060,7 +1060,7 @@ dev = [
     { name = "tomli", marker = "python_full_version == '3.10.*'", specifier = "==2.4.1" },
     { name = "typos", specifier = "==1.50.2" },
     { name = "uv", specifier = "==0.12.17" },
-    { name = "werkzeug", specifier = "==3.1.8" },
+    { name = "werkzeug", specifier = "==3.1.9" },
 ]
 pydantic-v1 = [{ name = "pydantic", specifier = "<2" }]
 pydantic-v2 = [{ name = "pydantic", specifier = ">=2" }]
@@ -1724,14 +1724,14 @@ wheels = [
 
 [[package]]
 name = "werkzeug"
-version = "3.1.8"
+version = "3.1.9"
 source = { registry = "https://pypi.org/simple" }
 dependencies = [
     { name = "markupsafe" },
 ]
-sdist = { url = "https://files.pythonhosted.org/packages/dd/b2/381be8cfdee792dd117872481b6e378f85c957dd7c5bca38897b08f765fd/werkzeug-3.1.8.tar.gz", hash = "sha256:9bad61a4268dac112f1c5cd4630a56ede601b6ed420300677a869083d70a4c44", size = 875852, upload-time = "2026-04-02T18:49:14.268Z" }
+sdist = { url = "https://files.pythonhosted.org/packages/a4/34/4dd12fc8bb7d61c91467ec3efe415ffa7d5456f799954b40c5bbaeae470e/werkzeug-3.1.9.tar.gz", hash = "sha256:55ca7c70a75689be937aa27f8ff4b018f06ff4838fc73045560bf0f5a1291060", size = 940188, upload-time = "2026-09-27T18:33:41.637Z" }
 wheels = [
-    { url = "https://files.pythonhosted.org/packages/93/8c/2e650f2afeb7ee576912636c23ddb621c91ac6a98e66dc8d29c3c69446e1/werkzeug-3.1.8-py3-none-any.whl", hash = "sha256:63a77fb8892bf28ebc3178683445222aa500e48ebad5ec77b0ad80f8726b1f50", size = 226459, upload-time = "2026-04-02T18:49:12.72Z" },
+    { url = "https://files.pythonhosted.org/packages/a1/38/df03f564f43cec2684823f3cccae1a652ee7face1cbaa76fb223096e64d7/werkzeug-3.1.9-py3-none-any.whl", hash = "sha256:6392e50c78460ba618e5b21f08a71f59c99ce99cdc6cf6e3dd7e6ccca8754fab", size = 228700, upload-time = "2026-09-27T18:33:39.685Z" },
 ]
 
 [[package]]