diff --git a/apps/user_ldap/lib/User/Manager.php b/apps/user_ldap/lib/User/Manager.php
index 539c667b8973c..0d83c29b7b4d2 100644
--- a/apps/user_ldap/lib/User/Manager.php
+++ b/apps/user_ldap/lib/User/Manager.php
@@ -166,8 +166,13 @@ function ($list, $attribute) {
 	 * @param string $id the Nextcloud username
 	 */
 	public function isDeletedUser(string $id): bool {
-		return $this->userConfig->getValueBool(
-			$id, 'user_ldap', 'isDeleted');
+		try {
+			return $this->userConfig->getValueBool($id, 'user_ldap', 'isDeleted');
+		} catch (\InvalidArgumentException $e) {
+			// Most likely the string is too long to be a valid user id
+			$this->logger->debug('Invalid id given to isDeletedUser', ['exception' => $e]);
+			return false;
+		}
 	}
 
 	/**
diff --git a/lib/private/Config/UserConfig.php b/lib/private/Config/UserConfig.php
index f7d135c134d7b..5a5488e34187e 100644
--- a/lib/private/Config/UserConfig.php
+++ b/lib/private/Config/UserConfig.php
@@ -1715,6 +1715,7 @@ private function isFlagged(int $needle, int $flags): bool {
 	 * @param bool $allowEmptyUser
 	 * @param bool $allowEmptyApp $app can be empty string
 	 * @param ValueType|null $valueType assert value type is only one type
+	 * @throws InvalidArgumentException if userId, app, or prefKey is invalid (too long, or empty string)
 	 */
 	private function assertParams(
 		string $userId = '',
diff --git a/lib/public/Config/IUserConfig.php b/lib/public/Config/IUserConfig.php
index ac9e67d569585..0c50c349d5a48 100644
--- a/lib/public/Config/IUserConfig.php
+++ b/lib/public/Config/IUserConfig.php
@@ -52,6 +52,7 @@ interface IUserConfig {
 	 * @param string $appId optional id of app
 	 *
 	 * @return list<string> list of userIds
+	 * @throws \InvalidArgumentException if $appId is invalid (too long)
 	 *
 	 * @since 32.0.0
 	 */
@@ -66,6 +67,7 @@ public function getUserIds(string $appId = ''): array;
 	 * @param string $userId id of the user
 	 *
 	 * @return list<string> list of app ids
+	 * @throws \InvalidArgumentException if $userId is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -81,6 +83,7 @@ public function getApps(string $userId): array;
 	 * @param string $app id of the app
 	 *
 	 * @return list<string> list of stored config keys
+	 * @throws \InvalidArgumentException if $userId or $app is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -95,6 +98,7 @@ public function getKeys(string $userId, string $app): array;
 	 * @param bool $lazy search within lazy loaded config
 	 *
 	 * @return bool TRUE if key exists
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -110,6 +114,7 @@ public function hasKey(string $userId, string $app, string $key, ?bool $lazy = f
 	 *
 	 * @return bool TRUE if value is sensitive
 	 * @throws UnknownKeyException if config key is not known
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -130,6 +135,7 @@ public function isSensitive(string $userId, string $app, string $key, ?bool $laz
 	 *
 	 * @return bool TRUE if value is sensitive
 	 * @throws UnknownKeyException if config key is not known
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -146,6 +152,7 @@ public function isIndexed(string $userId, string $app, string $key, ?bool $lazy
 	 *
 	 * @return bool TRUE if config is lazy loaded
 	 * @throws UnknownKeyException if config key is not known
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 * @see IUserConfig for details about lazy loading
 	 *
 	 * @since 32.0.0
@@ -164,6 +171,7 @@ public function isLazy(string $userId, string $app, string $key): bool;
 	 * @param bool $filtered filter sensitive config values
 	 *
 	 * @return array<string, string|int|float|bool|array> [key => value]
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -179,6 +187,7 @@ public function getValues(string $userId, string $app, string $prefix = '', bool
 	 * @param bool $filtered filter sensitive config values
 	 *
 	 * @return array<string, string|int|float|bool|array> [key => value]
+	 * @throws \InvalidArgumentException if $userId is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -194,6 +203,7 @@ public function getAllValues(string $userId, bool $filtered = false): array;
 	 * @param ValueType|null $typedAs enforce type for the returned values
 	 *
 	 * @return array<string, string|int|float|bool|array> [appId => value]
+	 * @throws \InvalidArgumentException if $userId or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -211,6 +221,7 @@ public function getValuesByApps(string $userId, string $key, bool $lazy = false,
 	 * @param array|null $userIds limit the search to a list of user ids
 	 *
 	 * @return array<string, string|int|float|bool|array> [userId => value]
+	 * @throws \InvalidArgumentException if $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -228,6 +239,7 @@ public function getValuesByUsers(string $app, string $key, ?ValueType $typedAs =
 	 * @param bool $caseInsensitive non-case-sensitive search, only works if $value is a string
 	 *
 	 * @return Generator<string>
+	 * @throws \InvalidArgumentException if $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -244,6 +256,7 @@ public function searchUsersByValueString(string $app, string $key, string $value
 	 * @param int $value config value
 	 *
 	 * @return Generator<string>
+	 * @throws \InvalidArgumentException if $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -260,6 +273,7 @@ public function searchUsersByValueInt(string $app, string $key, int $value): Gen
 	 * @param array $values list of possible config values
 	 *
 	 * @return Generator<string>
+	 * @throws \InvalidArgumentException if $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -276,6 +290,7 @@ public function searchUsersByValues(string $app, string $key, array $values): Ge
 	 * @param bool $value config value
 	 *
 	 * @return Generator<string>
+	 * @throws \InvalidArgumentException if $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -293,6 +308,7 @@ public function searchUsersByValueBool(string $app, string $key, bool $value): G
 	 * @param bool $lazy search within lazy loaded config
 	 *
 	 * @return string stored config value or $default if not set in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -316,6 +332,7 @@ public function getValueString(string $userId, string $app, string $key, string
 	 * @param bool $lazy search within lazy loaded config
 	 *
 	 * @return int stored config value or $default if not set in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -339,6 +356,7 @@ public function getValueInt(string $userId, string $app, string $key, int $defau
 	 * @param bool $lazy search within lazy loaded config
 	 *
 	 * @return float stored config value or $default if not set in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -362,6 +380,7 @@ public function getValueFloat(string $userId, string $app, string $key, float $d
 	 * @param bool $lazy search within lazy loaded config
 	 *
 	 * @return bool stored config value or $default if not set in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -385,6 +404,7 @@ public function getValueBool(string $userId, string $app, string $key, bool $def
 	 * @param bool $lazy search within lazy loaded config
 	 *
 	 * @return array stored config value or $default if not set in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -410,6 +430,7 @@ public function getValueArray(string $userId, string $app, string $key, array $d
 	 * @return ValueType type of the value
 	 * @throws UnknownKeyException if config key is not known
 	 * @throws IncorrectTypeException if config value type is not known
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -429,6 +450,7 @@ public function getValueType(string $userId, string $app, string $key, ?bool $la
 	 * @return int a bitflag in relation to the config value
 	 * @throws UnknownKeyException if config key is not known
 	 * @throws IncorrectTypeException if config value type is not known
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -450,6 +472,7 @@ public function getValueFlags(string $userId, string $app, string $key, bool $la
 	 * @param bool $lazy set config as lazy loaded
 	 *
 	 * @return bool TRUE if value was different, therefor updated in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -482,6 +505,7 @@ public function setValueString(string $userId, string $app, string $key, string
 	 * @param bool $lazy set config as lazy loaded
 	 *
 	 * @return bool TRUE if value was different, therefor updated in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -509,6 +533,7 @@ public function setValueInt(string $userId, string $app, string $key, int $value
 	 * @param bool $lazy set config as lazy loaded
 	 *
 	 * @return bool TRUE if value was different, therefor updated in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -535,6 +560,7 @@ public function setValueFloat(string $userId, string $app, string $key, float $v
 	 * @param bool $lazy set config as lazy loaded
 	 *
 	 * @return bool TRUE if value was different, therefor updated in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -562,6 +588,7 @@ public function setValueBool(string $userId, string $app, string $key, bool $val
 	 * @param bool $lazy set config as lazy loaded
 	 *
 	 * @return bool TRUE if value was different, therefor updated in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 *
@@ -584,6 +611,7 @@ public function setValueArray(string $userId, string $app, string $key, array $v
 	 * @param bool $sensitive TRUE to set as sensitive, FALSE to unset
 	 *
 	 * @return bool TRUE if database update were necessary
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -597,6 +625,7 @@ public function updateSensitive(string $userId, string $app, string $key, bool $
 	 * @param string $app id of the app
 	 * @param string $key config key
 	 * @param bool $sensitive TRUE to set as sensitive, FALSE to unset
+	 * @throws \InvalidArgumentException if $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -614,6 +643,7 @@ public function updateGlobalSensitive(string $app, string $key, bool $sensitive)
 	 * @param bool $indexed TRUE to set as indexed, FALSE to unset
 	 *
 	 * @return bool TRUE if database update were necessary
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -627,6 +657,7 @@ public function updateIndexed(string $userId, string $app, string $key, bool $in
 	 * @param string $app id of the app
 	 * @param string $key config key
 	 * @param bool $indexed TRUE to set as indexed, FALSE to unset
+	 * @throws \InvalidArgumentException if $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -641,6 +672,7 @@ public function updateGlobalIndexed(string $app, string $key, bool $indexed): vo
 	 * @param bool $lazy TRUE to set as lazy loaded, FALSE to unset
 	 *
 	 * @return bool TRUE if database update was necessary
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -654,6 +686,7 @@ public function updateLazy(string $userId, string $app, string $key, bool $lazy)
 	 * @param string $app id of the app
 	 * @param string $key config key
 	 * @param bool $lazy TRUE to set as lazy loaded, FALSE to unset
+	 * @throws \InvalidArgumentException if $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -680,6 +713,7 @@ public function updateGlobalLazy(string $app, string $key, bool $lazy): void;
 	 *
 	 * @return array
 	 * @throws UnknownKeyException if config key is not known in database
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -691,6 +725,7 @@ public function getDetails(string $userId, string $app, string $key): array;
 	 * @param string $userId id of the user
 	 * @param string $app id of the app
 	 * @param string $key config key
+	 * @throws \InvalidArgumentException if $userId, $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -701,6 +736,7 @@ public function deleteUserConfig(string $userId, string $app, string $key): void
 	 *
 	 * @param string $app id of the app
 	 * @param string $key config key
+	 * @throws \InvalidArgumentException if $app or $key is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -710,6 +746,7 @@ public function deleteKey(string $app, string $key): void;
 	 * delete all config keys linked to an app
 	 *
 	 * @param string $app id of the app
+	 * @throws \InvalidArgumentException if $app is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -719,6 +756,7 @@ public function deleteApp(string $app): void;
 	 * delete all config keys linked to a user
 	 *
 	 * @param string $userId id of the user
+	 * @throws \InvalidArgumentException if $userId is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */
@@ -731,6 +769,7 @@ public function deleteAllUserConfig(string $userId): void;
 	 *
 	 * @param string $userId id of the user
 	 * @param bool $reload set to TRUE to refill cache instantly after clearing it
+	 * @throws \InvalidArgumentException if $userId is invalid (too long, or empty string)
 	 *
 	 * @since 32.0.0
 	 */