diff --git a/README.md b/README.md
index fff6be2..913f0ef 100644
--- a/README.md
+++ b/README.md
@@ -161,8 +161,9 @@ python 3.13
     version-file: ".tool-versions"
 ```
 
-Only a single Python version is supported. Multiple fallback versions and the asdf `ref:`, `path:`,
-and `system` forms are ignored with a warning.
+Only a single Python version is supported. Filesystem paths are not supported for uv or Python.
+Multiple Python fallback versions and the asdf `ref:`, `path:`, and `system` forms are ignored with
+a warning.
 
 ```yaml
 - name: Install the latest version of uv and set the python version to 3.13t
diff --git a/__tests__/version/tool-versions-file.test.ts b/__tests__/version/tool-versions-file.test.ts
index bf91b0f..8276dca 100644
--- a/__tests__/version/tool-versions-file.test.ts
+++ b/__tests__/version/tool-versions-file.test.ts
@@ -113,6 +113,20 @@ describe("getUvVersionFromToolVersions", () => {
     );
   });
 
+  it.each(["/my/python/exploit", "my/exploited/uv", "C:\\exploited\\uv"])(
+    "should warn and return undefined for path %s",
+    async (version) => {
+      mockReadFileSync.mockReturnValue(`uv ${version}`);
+
+      const result = await getVersionFromToolVersions(".tool-versions");
+
+      expect(result).toBeUndefined();
+      expect(mockWarning).toHaveBeenCalledWith(
+        `The uv version ${version} in .tool-versions is not supported. Paths are not allowed.`,
+      );
+    },
+  );
+
   it("should handle file path with .tool-versions extension", async () => {
     const fileContent = "uv 0.1.0";
     mockReadFileSync.mockReturnValue(fileContent);
@@ -170,19 +184,23 @@ describe("getPythonVersionFromToolVersions", () => {
     );
   });
 
-  it.each(["ref:main", "path:~/src/python", "system"])(
-    "should warn and return undefined for %s",
-    async (version) => {
-      mockReadFileSync.mockReturnValue(`python ${version}`);
+  it.each([
+    "ref:main",
+    "path:~/src/python",
+    "system",
+    "/my/python/exploit",
+    "my/exploited/python",
+    "C:\\exploited\\python",
+  ])("should warn and return undefined for %s", async (version) => {
+    mockReadFileSync.mockReturnValue(`python ${version}`);
 
-      const result = await getPythonVersionFromToolVersions(".tool-versions");
+    const result = await getPythonVersionFromToolVersions(".tool-versions");
 
-      expect(result).toBeUndefined();
-      expect(mockWarning).toHaveBeenCalledWith(
-        `The Python version ${version} in .tool-versions is not supported. The Python entry will be ignored.`,
-      );
-    },
-  );
+    expect(result).toBeUndefined();
+    expect(mockWarning).toHaveBeenCalledWith(
+      `The Python version ${version} in .tool-versions is not supported. The Python entry will be ignored.`,
+    );
+  });
 
   it("should return undefined for non-.tool-versions files", async () => {
     const result = await getPythonVersionFromToolVersions(".python-version");
diff --git a/dist/save-cache/index.cjs b/dist/save-cache/index.cjs
index a1dbbda..9d78a0f 100644
--- a/dist/save-cache/index.cjs
+++ b/dist/save-cache/index.cjs
@@ -61862,7 +61862,7 @@ function getPythonVersionFromToolVersions(filePath) {
     return void 0;
   }
   const version3 = stripVersionPrefix(versions[0]);
-  if (version3 === "system" || version3.startsWith("ref:") || version3.startsWith("path:")) {
+  if (version3 === "system" || version3.startsWith("ref:") || version3.startsWith("path:") || isPath(version3)) {
     warning(
       `The Python version ${versions[0]} in .tool-versions is not supported. The Python entry will be ignored.`
     );
@@ -61890,6 +61890,9 @@ function getToolVersions(filePath, toolName) {
 function stripVersionPrefix(version3) {
   return version3.startsWith("v") ? version3.slice(1) : version3;
 }
+function isPath(version3) {
+  return version3.includes("/") || version3.includes("\\");
+}
 
 // src/utils/config-file.ts
 var import_node_fs3 = __toESM(require("node:fs"), 1);
diff --git a/dist/setup/index.cjs b/dist/setup/index.cjs
index f8d33d2..6f021ac 100644
--- a/dist/setup/index.cjs
+++ b/dist/setup/index.cjs
@@ -99245,6 +99245,12 @@ function getUvVersionFromToolVersions(filePath) {
     return void 0;
   }
   const version3 = stripVersionPrefix(versions[0]);
+  if (isPath(version3)) {
+    warning(
+      `The uv version ${versions[0]} in .tool-versions is not supported. Paths are not allowed.`
+    );
+    return void 0;
+  }
   if (version3.startsWith("ref")) {
     warning(
       "The ref syntax of .tool-versions is not supported. Please use a released version instead."
@@ -99265,7 +99271,7 @@ function getPythonVersionFromToolVersions(filePath) {
     return void 0;
   }
   const version3 = stripVersionPrefix(versions[0]);
-  if (version3 === "system" || version3.startsWith("ref:") || version3.startsWith("path:")) {
+  if (version3 === "system" || version3.startsWith("ref:") || version3.startsWith("path:") || isPath(version3)) {
     warning(
       `The Python version ${versions[0]} in .tool-versions is not supported. The Python entry will be ignored.`
     );
@@ -99293,6 +99299,9 @@ function getToolVersions(filePath, toolName) {
 function stripVersionPrefix(version3) {
   return version3.startsWith("v") ? version3.slice(1) : version3;
 }
+function isPath(version3) {
+  return version3.includes("/") || version3.includes("\\");
+}
 
 // src/version/uv-lock-file.ts
 var import_node_fs5 = __toESM(require("node:fs"), 1);
diff --git a/src/version/tool-versions-file.ts b/src/version/tool-versions-file.ts
index c18abcc..760ead0 100644
--- a/src/version/tool-versions-file.ts
+++ b/src/version/tool-versions-file.ts
@@ -10,6 +10,12 @@ export function getUvVersionFromToolVersions(
   }
 
   const version = stripVersionPrefix(versions[0]);
+  if (isPath(version)) {
+    core.warning(
+      `The uv version ${versions[0]} in .tool-versions is not supported. Paths are not allowed.`,
+    );
+    return undefined;
+  }
   if (version.startsWith("ref")) {
     core.warning(
       "The ref syntax of .tool-versions is not supported. Please use a released version instead.",
@@ -37,7 +43,8 @@ export function getPythonVersionFromToolVersions(
   if (
     version === "system" ||
     version.startsWith("ref:") ||
-    version.startsWith("path:")
+    version.startsWith("path:") ||
+    isPath(version)
   ) {
     core.warning(
       `The Python version ${versions[0]} in .tool-versions is not supported. The Python entry will be ignored.`,
@@ -73,3 +80,7 @@ function getToolVersions(
 function stripVersionPrefix(version: string): string {
   return version.startsWith("v") ? version.slice(1) : version;
 }
+
+function isPath(version: string): boolean {
+  return version.includes("/") || version.includes("\\");
+}