diff --git a/Jellyfin.Api/Controllers/AudioController.cs b/Jellyfin.Api/Controllers/AudioController.cs
index cd09d2bfab..72be555133 100644
--- a/Jellyfin.Api/Controllers/AudioController.cs
+++ b/Jellyfin.Api/Controllers/AudioController.cs
@@ -91,18 +91,18 @@ public class AudioController : BaseJellyfinApiController
     [ProducesAudioFile]
     public async Task<ActionResult> GetAudioStream(
         [FromRoute, Required] Guid itemId,
-        [FromQuery] string? container,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? container,
         [FromQuery] bool? @static,
         [FromQuery] string? @params,
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -132,8 +132,8 @@ public class AudioController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
@@ -261,12 +261,12 @@ public class AudioController : BaseJellyfinApiController
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -296,8 +296,8 @@ public class AudioController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
diff --git a/Jellyfin.Api/Controllers/DynamicHlsController.cs b/Jellyfin.Api/Controllers/DynamicHlsController.cs
index e5be48b808..49fc2f3d78 100644
--- a/Jellyfin.Api/Controllers/DynamicHlsController.cs
+++ b/Jellyfin.Api/Controllers/DynamicHlsController.cs
@@ -163,18 +163,18 @@ public class DynamicHlsController : BaseJellyfinApiController
     [ProducesPlaylistFile]
     public async Task<ActionResult> GetLiveHlsStream(
         [FromRoute, Required] Guid itemId,
-        [FromQuery] string? container,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? container,
         [FromQuery] bool? @static,
         [FromQuery] string? @params,
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -204,8 +204,8 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
@@ -406,12 +406,12 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery, Required] string mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -443,8 +443,8 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
@@ -577,12 +577,12 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery, Required] string mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -613,8 +613,8 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
@@ -742,12 +742,12 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -779,8 +779,8 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
@@ -909,12 +909,12 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -945,8 +945,8 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
@@ -1085,12 +1085,12 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -1122,8 +1122,8 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
@@ -1265,12 +1265,12 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -1301,8 +1301,8 @@ public class DynamicHlsController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
diff --git a/Jellyfin.Api/Controllers/UniversalAudioController.cs b/Jellyfin.Api/Controllers/UniversalAudioController.cs
index 634fca2eb1..db78e99464 100644
--- a/Jellyfin.Api/Controllers/UniversalAudioController.cs
+++ b/Jellyfin.Api/Controllers/UniversalAudioController.cs
@@ -92,13 +92,13 @@ public class UniversalAudioController : BaseJellyfinApiController
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
         [FromQuery] Guid? userId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] int? maxAudioChannels,
         [FromQuery] int? transcodingAudioChannels,
         [FromQuery] int? maxStreamingBitrate,
         [FromQuery] int? audioBitRate,
         [FromQuery] long? startTimeTicks,
-        [FromQuery] string? transcodingContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? transcodingContainer,
         [FromQuery] MediaStreamProtocol? transcodingProtocol,
         [FromQuery] int? maxAudioSampleRate,
         [FromQuery] int? maxAudioBitDepth,
diff --git a/Jellyfin.Api/Controllers/VideosController.cs b/Jellyfin.Api/Controllers/VideosController.cs
index b3029d6fa8..3801200320 100644
--- a/Jellyfin.Api/Controllers/VideosController.cs
+++ b/Jellyfin.Api/Controllers/VideosController.cs
@@ -311,18 +311,18 @@ public class VideosController : BaseJellyfinApiController
     [ProducesVideoFile]
     public async Task<ActionResult> GetVideoStream(
         [FromRoute, Required] Guid itemId,
-        [FromQuery] string? container,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? container,
         [FromQuery] bool? @static,
         [FromQuery] string? @params,
         [FromQuery] string? tag,
         [FromQuery, ParameterObsolete] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -354,8 +354,8 @@ public class VideosController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
@@ -555,12 +555,12 @@ public class VideosController : BaseJellyfinApiController
         [FromQuery] string? tag,
         [FromQuery] string? deviceProfileId,
         [FromQuery] string? playSessionId,
-        [FromQuery] string? segmentContainer,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? segmentContainer,
         [FromQuery] int? segmentLength,
         [FromQuery] int? minSegments,
         [FromQuery] string? mediaSourceId,
         [FromQuery] string? deviceId,
-        [FromQuery] string? audioCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? audioCodec,
         [FromQuery] bool? enableAutoStreamCopy,
         [FromQuery] bool? allowVideoStreamCopy,
         [FromQuery] bool? allowAudioStreamCopy,
@@ -592,8 +592,8 @@ public class VideosController : BaseJellyfinApiController
         [FromQuery] int? cpuCoreLimit,
         [FromQuery] string? liveStreamId,
         [FromQuery] bool? enableMpegtsM2TsMode,
-        [FromQuery] string? videoCodec,
-        [FromQuery] string? subtitleCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? videoCodec,
+        [FromQuery] [RegularExpression(EncodingHelper.ValidationRegex)] string? subtitleCodec,
         [FromQuery] string? transcodeReasons,
         [FromQuery] int? audioStreamIndex,
         [FromQuery] int? videoStreamIndex,
diff --git a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
index 178a9999c8..9a0e4a62cb 100644
--- a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
+++ b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
@@ -1,6 +1,8 @@
 #nullable disable
 
 #pragma warning disable CS1591
+// We need lowercase normalized string for ffmpeg
+#pragma warning disable CA1308
 
 using System;
 using System.Collections.Generic;
@@ -26,6 +28,14 @@ namespace MediaBrowser.Controller.MediaEncoding
 {
     public partial class EncodingHelper
     {
+        /// <summary>
+        /// The codec validation regex.
+        /// This regular expression matches strings that consist of alphanumeric characters, hyphens,
+        /// periods, underscores, commas, and vertical bars, with a length between 0 and 40 characters.
+        /// This should matches all common valid codecs.
+        /// </summary>
+        public const string ValidationRegex = @"^[a-zA-Z0-9\-\._,|]{0,40}$";
+
         private const string QsvAlias = "qs";
         private const string VaapiAlias = "va";
         private const string D3d11vaAlias = "dx11";
@@ -53,6 +63,8 @@ namespace MediaBrowser.Controller.MediaEncoding
         private readonly Version _minFFmpegVaapiH26xEncA53CcSei = new Version(6, 0);
         private readonly Version _minFFmpegReadrateOption = new Version(5, 0);
 
+        private static readonly Regex _validationRegex = new(ValidationRegex, RegexOptions.Compiled);
+
         private static readonly string[] _videoProfilesH264 = new[]
         {
             "ConstrainedBaseline",
@@ -391,7 +403,10 @@ namespace MediaBrowser.Controller.MediaEncoding
                     return "libtheora";
                 }
 
-                return codec.ToLowerInvariant();
+                if (_validationRegex.IsMatch(codec))
+                {
+                    return codec.ToLowerInvariant();
+                }
             }
 
             return "copy";
@@ -429,7 +444,7 @@ namespace MediaBrowser.Controller.MediaEncoding
 
         public static string GetInputFormat(string container)
         {
-            if (string.IsNullOrEmpty(container))
+            if (string.IsNullOrEmpty(container) || !_validationRegex.IsMatch(container))
             {
                 return null;
             }
@@ -685,6 +700,11 @@ namespace MediaBrowser.Controller.MediaEncoding
         {
             var codec = state.OutputAudioCodec;
 
+            if (!_validationRegex.IsMatch(codec))
+            {
+                codec = "aac";
+            }
+
             if (string.Equals(codec, "aac", StringComparison.OrdinalIgnoreCase))
             {
                 // Use Apple's aac encoder if available as it provides best audio quality