diff --git a/src/NzbDrone.Common.Test/Http/CookieUtilFixture.cs b/src/NzbDrone.Common.Test/Http/CookieUtilFixture.cs
new file mode 100644
index 000000000..970633966
--- /dev/null
+++ b/src/NzbDrone.Common.Test/Http/CookieUtilFixture.cs
@@ -0,0 +1,101 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using NUnit.Framework;
+using NzbDrone.Common.Http;
+
+namespace NzbDrone.Common.Test.Http
+{
+    [TestFixture]
+    public class CookieUtilFixture
+    {
+        [Test]
+        public void CookieHeaderToDictionaryGood()
+        {
+            // valid cookies with non-alpha characters in the value
+            var cookieHeader = "__cfduid=d6237f041586694295; __cf_bm=TlOng/xyqckk-TMen38z+0RFYA7YA=";
+            var expectedCookieDictionary = new Dictionary<string, string>
+            {
+                { "__cfduid", "d6237f041586694295" },
+                { "__cf_bm", "TlOng/xyqckk-TMen38z+0RFYA7YA=" }
+            };
+            CollectionAssert.AreEqual(expectedCookieDictionary, CookieUtil.CookieHeaderToDictionary(cookieHeader));
+        }
+
+        [Test]
+        public void CookieHeaderToDictionaryDuplicateKeys()
+        {
+            // cookie with duplicate keys and whitespace separator instead of ;
+            var cookieHeader = "__cfduid=d6237f041586694295; __cf_bm=TlOng/xyqckk-TMen38z+0RFYA7YA= __cf_bm=test";
+            var expectedCookieDictionary = new Dictionary<string, string>
+            {
+                { "__cfduid", "d6237f041586694295" },
+                { "__cf_bm", "test" } // we always assume the latest value is the most recent
+            };
+            CollectionAssert.AreEqual(expectedCookieDictionary, CookieUtil.CookieHeaderToDictionary(cookieHeader));
+        }
+
+        [Test]
+        public void CookieHeaderToDictionaryMalformed()
+        {
+            // malformed cookies
+            var cookieHeader = "__cfduidd6237f041586694295; __cf_;bm TlOng; good_cookie=value";
+            var expectedCookieDictionary = new Dictionary<string, string> { { "good_cookie", "value" }, };
+            CollectionAssert.AreEqual(expectedCookieDictionary, CookieUtil.CookieHeaderToDictionary(cookieHeader));
+        }
+
+        [Test]
+        [SuppressMessage("ReSharper", "CollectionNeverUpdated.Local")]
+        public void CookieHeaderToDictionaryNull()
+        {
+            // null cookie header
+            var expectedCookieDictionary = new Dictionary<string, string>();
+            CollectionAssert.AreEqual(expectedCookieDictionary, CookieUtil.CookieHeaderToDictionary(null));
+        }
+
+        [Test]
+        public void CookieDictionaryToHeaderGood()
+        {
+            // valid cookies with non-alpha characters in the value
+            var cookieDictionary = new Dictionary<string, string>
+            {
+                { "__cfduid", "d6237f041586694295" },
+                { "__cf_bm", "TlOng/xyqckk-TMen38z+0RFYA7YA=" }
+            };
+            var expectedCookieHeader = "__cfduid=d6237f041586694295; __cf_bm=TlOng/xyqckk-TMen38z+0RFYA7YA=";
+            CollectionAssert.AreEqual(expectedCookieHeader, CookieUtil.CookieDictionaryToHeader(cookieDictionary));
+        }
+
+        [Test]
+        public void CookieDictionaryToHeaderMalformed1()
+        {
+            // malformed key
+            var cookieDictionary = new Dictionary<string, string>
+            {
+                { "__cf_=bm", "34234234" }
+            };
+            var ex = Assert.Throws<FormatException>(() => CookieUtil.CookieDictionaryToHeader(cookieDictionary));
+            Assert.AreEqual("The cookie '__cf_=bm=34234234' is malformed.", ex.Message);
+        }
+
+        [Test]
+        public void CookieDictionaryToHeaderMalformed2()
+        {
+            // malformed value
+            var cookieDictionary = new Dictionary<string, string>
+            {
+                { "__cf_bm", "34234 234" }
+            };
+            var ex = Assert.Throws<FormatException>(() => CookieUtil.CookieDictionaryToHeader(cookieDictionary));
+            Assert.AreEqual("The cookie '__cf_bm=34234 234' is malformed.", ex.Message);
+        }
+
+        [Test]
+        public void CookieDictionaryToHeaderNull()
+        {
+            // null cookie dictionary
+            var expectedCookieHeader = "";
+            CollectionAssert.AreEqual(expectedCookieHeader, CookieUtil.CookieDictionaryToHeader(null));
+        }
+    }
+}
diff --git a/src/NzbDrone.Common/Http/CookieUtil.cs b/src/NzbDrone.Common/Http/CookieUtil.cs
index 38c3c756b..ea408989a 100644
--- a/src/NzbDrone.Common/Http/CookieUtil.cs
+++ b/src/NzbDrone.Common/Http/CookieUtil.cs
@@ -9,7 +9,7 @@ namespace NzbDrone.Common.Http
     {
         // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie
         // NOTE: we are not checking non-ascii characters and we should
-        private static readonly Regex _CookieRegex = new Regex(@"([^\(\)<>@,;:\\""/\[\]\?=\{\}\s]+)=([^,;\\""\s]+)");
+        private static readonly Regex CookieRegex = new (@"([^\(\)<>@,;:\\""/\[\]\?=\{\}\s]+)=([^,;\\""\s]+)");
         private static readonly string[] FilterProps = { "COMMENT", "COMMENTURL", "DISCORD", "DOMAIN", "EXPIRES", "MAX-AGE", "PATH", "PORT", "SECURE", "VERSION", "HTTPONLY", "SAMESITE" };
         private static readonly char[] InvalidKeyChars = { '(', ')', '<', '>', '@', ',', ';', ':', '\\', '"', '/', '[', ']', '?', '=', '{', '}', ' ', '\t', '\n' };
         private static readonly char[] InvalidValueChars = { '"', ',', ';', '\\', ' ', '\t', '\n' };
@@ -22,7 +22,7 @@ namespace NzbDrone.Common.Http
                 return cookieDictionary;
             }
 
-            var matches = _CookieRegex.Match(cookieHeader);
+            var matches = CookieRegex.Match(cookieHeader);
             while (matches.Success)
             {
                 if (matches.Groups.Count > 2 && !FilterProps.Contains(matches.Groups[1].Value.ToUpperInvariant()))