diff --git a/src/core/utils/glob.spec.ts b/src/core/utils/glob.spec.ts
index 6951827b..5b79955c 100644
--- a/src/core/utils/glob.spec.ts
+++ b/src/core/utils/glob.spec.ts
@@ -1,4 +1,4 @@
-import { globToRegExp } from "./glob";
+import { globToRegExp, isBalancedCurlyBrackets, isValidGlobExpression } from "./glob";
 
 describe("globToRegExp()", () => {
   it("glob = <empty>", () => {
@@ -24,19 +24,95 @@ describe("globToRegExp()", () => {
     expect(globToRegExp("/foo/*")).toBe("\\/foo\\/.*");
   });
 
-  it("glob = /*.{jpg}", () => {
-    expect(globToRegExp("/*.{jpg}")).toBe("\\/.*(jpg)");
+  it("glob = /*.{ext}", () => {
+    expect(globToRegExp("/*.{ext}")).toBe("\\/.*(ext)");
   });
 
-  it("glob = /*.{jpg,gif}", () => {
-    expect(globToRegExp("/*.{jpg,gif}")).toBe("\\/.*(jpg|gif)");
+  it("glob = /*.{ext,gif}", () => {
+    expect(globToRegExp("/*.{ext,gif}")).toBe("\\/.*(ext|gif)");
   });
 
-  it("glob = /foo/*.{jpg,gif}", () => {
-    expect(globToRegExp("/foo/*.{jpg,gif}")).toBe("\\/foo\\/.*(jpg|gif)");
+  it("glob = /foo/*.{ext,gif}", () => {
+    expect(globToRegExp("/foo/*.{ext,gif}")).toBe("\\/foo\\/.*(ext|gif)");
   });
 
   it("glob = {foo,bar}.json", () => {
     expect(globToRegExp("{foo,bar}.json")).toBe("(foo|bar).json");
   });
 });
+
+// describe isValidGlobExpression
+
+describe("isValidGlobExpression()", () => {
+  // valid expressions
+  ["*", "/*", "/foo/*", "/foo/*.ext", "/*.ext", "*.ext", "/foo/*.ext", "/foo/*.{ext}", "/foo/*.{ext,ext}"].forEach((glob) => {
+    describe("should be TRUE for the following values", () => {
+      it(`glob = ${glob}`, () => {
+        expect(isValidGlobExpression(glob)).toBe(true);
+      });
+    });
+  });
+
+  // invalid expressions
+  [
+    undefined,
+    "",
+    "*.*",
+    "**.*",
+    "**.**",
+    "**",
+    "*/*",
+    "*/*.ext",
+    "*.ext/*",
+    "*/*.ext*",
+    "*.ext/*.ext",
+    "/blog/*/management",
+    "/foo/*.{ext,,,,}",
+    "/foo/*.{ext,",
+    "/foo/*.ext,}",
+    "/foo/*.ext}",
+    "/foo/*.{}",
+    "/foo/*.",
+    "/foo/.",
+  ].forEach((glob) => {
+    describe("should be FALSE for the following values", () => {
+      it(`glob = ${glob}`, () => {
+        expect(isValidGlobExpression(glob)).toBe(false);
+      });
+    });
+  });
+});
+
+describe("isBalancedCurlyBrackets()", () => {
+  it("should be true for {}", () => {
+    expect(isBalancedCurlyBrackets("{,,,}")).toBe(true);
+  });
+
+  it("should be true for {}{}{}", () => {
+    expect(isBalancedCurlyBrackets("{,,,}{,,,}{,,,}")).toBe(true);
+  });
+
+  it("should be true for {{}}", () => {
+    expect(isBalancedCurlyBrackets("{,,,{,,,},,,}")).toBe(true);
+  });
+
+  it("should be false for }{", () => {
+    expect(isBalancedCurlyBrackets("},,,{")).toBe(false);
+  });
+
+  it("should be false for }{}{", () => {
+    expect(isBalancedCurlyBrackets("},,,{,,,},,,{")).toBe(false);
+  });
+
+  it("should be false for {", () => {
+    expect(isBalancedCurlyBrackets("{,,,")).toBe(false);
+  });
+
+  it("should be false for }", () => {
+    expect(isBalancedCurlyBrackets(",,,}")).toBe(false);
+  });
+
+  it("should be false for {}}{{}", () => {
+    expect(isBalancedCurlyBrackets("{,,,}},,,{{,,,}")).toBe(false);
+  });
+});
diff --git a/src/core/utils/glob.ts b/src/core/utils/glob.ts
index 5e2ae658..7c0f8866 100644
--- a/src/core/utils/glob.ts
+++ b/src/core/utils/glob.ts
@@ -2,7 +2,10 @@ import chalk from "chalk";
 import { logger } from "./logger";
 
 /**
- *  Turn expression into a valid regex
+ * Turn expression into a valid regexp
+ *
+ * @param glob A string containing a valid wildcard expression
+ * @returns a string containing a valid RegExp
  */
 export function globToRegExp(glob: string | undefined) {
   logger.silly(`turning glob expression into valid RegExp`);
@@ -25,3 +28,88 @@ export function globToRegExp(glob: string | undefined) {
 
   return glob.replace(/\//g, "\\/").replace("*.", ".*").replace("/*", "/.*");
 }
+
+/**
+ * Check if the route rule contains a valid wildcard expression
+ *
+ * @param glob A string containing a valid wildcard expression
+ * @returns true if the glob expression is valid, false otherwise
+ * @see https://docs.microsoft.com/azure/static-web-apps/configuration#wildcards
+ */
+export function isValidGlobExpression(glob: string | undefined) {
+  logger.silly(`checking if glob expression is valid`);
+  logger.silly(` - glob: ${chalk.yellow(glob)}`);
+
+  if (!glob) {
+    logger.silly(` - glob is empty. Return false`);
+    return false;
+  }
+
+  if (glob === "*") {
+    logger.silly(` - glob is *`);
+    return true;
+  }
+
+  const hasWildcard = glob.includes("*");
+
+  if (hasWildcard) {
+    const paths = glob.split("*");
+    if (paths.length > 2) {
+      logger.silly(` - glob has more than one wildcard. Return false`);
+      return false;
+    }
+
+    const pathBeforeWildcard = paths[0];
+    if (pathBeforeWildcard && glob.endsWith("*")) {
+      logger.silly(` - glob ends with *. Return true`);
+      return true;
+    }
+
+    const pathAfterWildcard = paths[1];
+    if (pathAfterWildcard) {
+      logger.silly(` - pathAfterWildcard: ${chalk.yellow(pathAfterWildcard)}`);
+
+      if (isBalancedCurlyBrackets(glob) === false) {
+        logger.silly(` - pathAfterWildcard contains unbalanced { } syntax. Return false`);
+        return false;
+      }
+
+      // match exactly extensions of type:
+      // -->  /blog/*.html
+      // --> /blog/*.{html,jpg}
+      const filesExtensionMatch = pathAfterWildcard.match(/\.(\w+|\{\w+(,\w+)*\})$/);
+
+      if (filesExtensionMatch) {
+        logger.silly(`  - pathAfterWildcard match a file extension. Return true`);
+        return true;
+      } else {
+        logger.silly(`  - pathAfterWildcard doesn't match a file extension. Return false`);
+        return false;
+      }
+    }
+  }
+
+  return false;
+}
+
+/**
+ * Checks if a string expression has balanced curly brackets
+ *
+ * @param str the string expression to be checked
+ * @returns true if the string expression has balanced curly brackets, false otherwise
+ */
+export function isBalancedCurlyBrackets(str: string) {
+  const stack = [];
+  for (let i = 0; i < str.length; i++) {
+    const char = str[i];
+    if (char === "{") {
+      stack.push(char);
+    } else if (char === "}") {
+      if (stack.length === 0) {
+        return false;
+      }
+      stack.pop();
+    }
+  }
+  return stack.length === 0;
+}
diff --git a/src/msha/routes-engine/route-processor.ts b/src/msha/routes-engine/route-processor.ts
index 2d09e799..8bb49362 100644
--- a/src/msha/routes-engine/route-processor.ts
+++ b/src/msha/routes-engine/route-processor.ts
@@ -3,7 +3,7 @@ import chalk from "chalk";
 import { DEFAULT_CONFIG } from "../../config";
 import { logger } from "../../core";
 import { AUTH_STATUS, SWA_CLI_APP_PROTOCOL } from "../../core/constants";
-import { globToRegExp } from "../../core/utils/glob";
+import { globToRegExp, isValidGlobExpression } from "../../core/utils/glob";
 import { getIndexHtml } from "./rules/routes";
 
 export function doesRequestPathMatchRoute(
@@ -46,7 +46,7 @@ export function doesRequestPathMatchRoute(
     return true;
   }
 
-  // Since this is a file request, return now, since tring to get a match by appending /index.html doesn't apply here
+  // Since this is a file request, return now, since we are trying to get a match by appending /index.html doesn't apply here
   if (!route) {
     logger.silly(` - route: ${chalk.yellow(route || "<empty>")}`);
     logger.silly(` - match: ${chalk.yellow(false)}`);
@@ -100,11 +100,17 @@ function doesRequestPathMatchWildcardRoute(requestPath: string, requestPathFileW
   // before processing regexp which might be expensive
   // let's check first if both path and rule start with the same substring
   if (pathBeforeWildcard && requestPath.startsWith(pathBeforeWildcard) === false) {
-    logger.silly(` - substring don't match. Exit`);
+    logger.silly(` - base path doesn't match. Exit`);
 
     return false;
   }
 
+  // also, let's check if the route rule doesn't contains a wildcard in the middle of the path
+  if (isValidGlobExpression(requestPathFileWithWildcard) === false) {
+    logger.silly(` - route rule contains a wildcard in the middle of the path. Exit`);
+    return false;
+  }
+
   // we don't support full globs in the config file.
   // add this little utility to convert a wildcard into a valid glob pattern
   const regexp = new RegExp(`^${globToRegExp(requestPathFileWithWildcard)}$`);
diff --git a/src/msha/routes-engine/rules/navigation-fallback.ts b/src/msha/routes-engine/rules/navigation-fallback.ts
index 397e28b5..f21ff434 100644
--- a/src/msha/routes-engine/rules/navigation-fallback.ts
+++ b/src/msha/routes-engine/rules/navigation-fallback.ts
@@ -3,7 +3,7 @@ import fs from "fs";
 import type http from "http";
 import path from "path";
 import { logger } from "../../../core";
-import { globToRegExp } from "../../../core/utils/glob";
+import { globToRegExp, isValidGlobExpression } from "../../../core/utils/glob";
 import { AUTH_STATUS } from "../../../core/constants";
 import { doesRequestPathMatchRoute } from "../route-processor";
 import { getIndexHtml } from "./routes";
@@ -50,12 +50,18 @@ export function navigationFallback(req: http.IncomingMessage, res: http.ServerRe
 
   // parse the exclusion rules and match at least one rule
   const isMatchedExcludeRule = navigationFallback?.exclude?.some((filter) => {
+    if (isValidGlobExpression(filter) === false) {
+      logger.silly(` - invalid rule ${chalk.yellow(filter)}`);
+      logger.silly(` - mark as no match`);
+      return false;
+    }
+
     // we don't support full globs in the config file.
     // add this little utility to convert a wildcard into a valid glob pattern
     const regexp = new RegExp(`^${globToRegExp(filter)}$`);
     const isMatch = regexp.test(originlUrl!);
 
-    logger.silly(`   - exclude: ${chalk.yellow(filter)}`);
+    logger.silly(`   - rule: ${chalk.yellow(filter)}`);
     logger.silly(`   - regexp: ${chalk.yellow(regexp)}`);
     logger.silly(`   - isRegexpMatch: ${chalk.yellow(isMatch)}`);