CVE-2026-24061: Віддалене обходження аутентифікації в GNU InetUtils Telnetd

Ruslan Mikhalov Керівник досліджень загроз у SOC Prime

Стежити

CVE-2026-24061: Віддалене обходження аутентифікації в GNU InetUtils Telnetd

Detection stack

AIDR
Alert
ETL
Query

Звіт про загрози
Потік атаки
Виявлення
Симуляції

Резюме

CVE-2026-24061 — це віддалене обхід автентифікації у GNU InetUtils telnetd, що впливає на версії від 1.9.3 до 2.7. Неавтентифікований зловмисник може надати спеціально сформовану змінну середовища USER і передати її через клієнт telnet з використанням опцій -a або –login, що дозволяє входити в систему з рівнем доступу root. Проблема оцінюється як CVSS 9.8. Сфера дії обмежена до GNU InetUtils telnetd (до версії 2.7); інші реалізації telnetd (включаючи Cisco IOS, Microsoft, Netkit та BusyBox) не підпадають під вплив. Успішна експлуатація забезпечує віддалений доступ і може також використовуватись для локального підвищення привілеїв до root. Найбезпечніше вирішення — виявити і повністю вимкнути Telnet, мережеві обмеження можуть зменшити експозицію, але лише видалення служби повністю усуває ризик локального підвищення привілеїв до root.

Розслідування

NSFOCUS CERT визначив, що telnetd не правильно перевіряє змінну середовища USER, надану клієнтом. Зловмисник може скористатися цією слабкістю перевірки для обходу стандартної логіки автентифікації та отримати доступ до root на вразливих Linux/Unix системах, що працюють з уразливим демоном.

Пом’якшення

Доступна виправлення від постачальника для GNU InetUtils; уразливі системи повинні оновитися до виправленого випуску. Якщо негайне виправлення неможливе, вимкніть telnetd і перейдіть на SSH. Додаткові проміжні заходи включають налаштування telnetd для використання спеціальної оболонки входу і вимкнення або запобігання використанню параметра -f, де це можливо.

Відповідь

Визначіть системи, в яких працює telnetd, і відстежуйте сесії telnet, ініційовані з параметрами -a або –login, особливо коли спостерігаються віддалені спроби встановити змінну середовища USER. Пріоритезуйте розгортання виправлень, вимикайте telnetd де це можливо і запровадьте зашифровані протоколи віддаленого адміністрування, щоб запобігти повторній експлуатації.

Потік атаки

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Виявлення

Використання Telnet [Можлива активність LPE] (через cmdline)

SOC Prime Team

29 Січня 2026

Переглянути

Використання внутрішнього/зовнішнього порту Telnet (через auditd)

SOC Prime Team

29 Січня 2026

Переглянути

Використання внутрішнього/зовнішнього порту Telnet (через zeek)

SOC Prime Team

29 Січня 2026

Переглянути

Використання внутрішнього/зовнішнього порту Telnet (через firewall)

SOC Prime Team

29 Січня 2026

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Симуляція

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