peass-ng/PEASS-ng · error · ArgumentNullException

The array and none of the values passed as parameters may be

Error message

The array and none of the values passed as parameters may be `null`.

What it means

Task.RunEx() rejects a null parameters array or any null element inside it with an ArgumentNullException. The native IRegisteredTask::RunEx requires a valid string array, so the wrapper pre-validates the input.

Source

Thrown at winPEAS/winPEASexe/winPEAS/TaskScheduler/Task.cs:1477

        /// false for the task.
        /// </para>
        /// <para>If RunEx is invoked from a disabled task, it will return <c>null</c> and the task will not be run.</para>
        /// </remarks>
        /// <exception cref="NotV1SupportedException">Not supported under Task Scheduler 1.0.</exception>
        /// <example>
        /// <code lang="cs">
        ///<![CDATA[
        /// // Run the current task with a parameter as a different user and ignoring any of the conditions.
        /// var runningTask = myTaskInstance.RunEx(TaskRunFlags.IgnoreConstraints, 0, "DOMAIN\\User", "info");
        /// Console.Write(string.Format("Running task's current action is {0}.", runningTask.CurrentAction));
        ///]]>
        /// </code>
        /// </example>
        public RunningTask RunEx(TaskRunFlags flags, int sessionID, string user, params string[] parameters)
        {
            if (v2Task == null) throw new NotV1SupportedException();
            if (parameters == null || parameters.Any(s => s == null))
                throw new ArgumentNullException(nameof(parameters), "The array and none of the values passed as parameters may be `null`.");
            if (parameters.Length > 32)
                throw new ArgumentOutOfRangeException(nameof(parameters), "A maximum of 32 parameters can be supplied to RunEx.");
            if (TaskService.HighestSupportedVersion < TaskServiceVersion.V1_5 && parameters.Any(p => (p?.Length ?? 0) >= 260))
                throw new ArgumentOutOfRangeException(nameof(parameters), "On systems prior to Windows 10, no individual parameter may be more than 260 characters.");
            var irt = v2Task.RunEx(parameters.Length == 0 ? null : parameters, (int)flags, sessionID, user);
            return irt != null ? new RunningTask(TaskService, v2Task, irt) : null;
        }

        /// <summary>
        /// Applies access control list (ACL) entries described by a <see cref="TaskSecurity"/> object to the file described by the current
        /// <see cref="Task"/> object.
        /// </summary>
        /// <param name="taskSecurity">
        /// A <see cref="TaskSecurity"/> object that describes an access control list (ACL) entry to apply to the current task.
        /// </param>
        /// <example>
        /// <para>Give read access to all authenticated users for a task.</para>
        /// <code lang="cs">

View on GitHub (pinned to 53fb989abc)

Solutions

1. Ensure the params array and every element are non-null before calling RunEx
2. Filter or replace nulls: parameters.Where(p => p != null)
3. Coalesce nulls to empty strings if an empty argument is acceptable
4. Validate user/session inputs that feed the array so they cannot be null

Example fix

// before
task.RunEx(TaskRunFlags.Default, 0, user, arg1, arg2); // arg2 may be null
// after
task.RunEx(TaskRunFlags.Default, 0, user, arg1 ?? "", arg2 ?? "");

bool valid = parameters != null && parameters.All(p => p != null);
if (!valid) throw new ArgumentException("parameters array and elements must be non-null");

bool HasNoNulls(string[]? p) => p != null && Array.TrueForAll(p, s => s != null);

try { task.RunEx(flags, sid, user, parameters); }
catch (ArgumentNullException) { parameters = parameters?.Where(s => s != null).ToArray() ?? Array.Empty<string>(); }

When it happens

Trigger: Calling task.RunEx(flags, sessionID, user, null) or task.RunEx(flags, sessionID, user, "a", null) — i.e. the array itself is null or contains at least one null string.

Common situations: Building the parameter list dynamically from variables/config where one value is null; passing an uninitialized array; LINQ projections producing null entries.

Related errors

• Value cannot be null. (Parameter 'folderSecurity')
• Value cannot be null. Parameter name: path
• A maximum of 32 actions is allowed within a single task.
• Attachments array cannot contain more than 8 items.
• Each value of the array must contain a valid file reference.

AI-assisted analysis of peass-ng/PEASS-ng@53fb989abc (2026-09-02). Data as JSON: /api/errors/89918cae00e5107d. Report an issue: GitHub.