CVE-2020-25686

Se encontró un fallo en dnsmasq versiones anteriores a 2.83. Al recibir una consulta, dnsmasq no comprueba si existe una petición pendiente existente para el mismo nombre y reenvía una nueva petición. Por defecto, se puede enviar un máximo de 150 consultas pendientes a los servidores aguas arriba, por lo que puede haber como máximo 150 consultas para el mismo nombre. Este fallo permite a un atacante fuera de ruta en la red reduzca sustancialmente el número de intentos que tendría que realizar para falsificar una respuesta y hacer que dnsmasq la acepte. Este problema se menciona en la sección "Birthday Attacks" de RFC5452. Si se encadenaba con CVE-2020-25684, se reduce la complejidad del ataque de un ataque con éxito. La mayor amenaza de esta vulnerabilidad es la integridad de los datos

A flaw was found in dnsmasq. When receiving a query, dnsmasq does not check for an existing pending request for the same name and forwards a new request. By default, a maximum of 150 pending queries can be sent to upstream servers, so there can be at most 150 queries for the same name. This flaw allows an off-path attacker on the network to substantially reduce the number of attempts that it would have to perform to forge a reply and have it accepted by dnsmasq. This issue is mentioned in the "Birthday Attacks" section of RFC5452. If chained with CVE-2020-25684, the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.

USN-4698-1 fixed vulnerabilities in Dnsmasq. The updates introduced regressions in certain environments related to issues with multiple queries, and issues with retries. This update fixes the problem. Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly handled memory when sorting RRsets. A remote attacker could use this issue to cause Dnsmasq to hang, resulting in a denial of service, or possibly execute arbitrary code. Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly handled extracting certain names. A remote attacker could use this issue to cause Dnsmasq to hang, resulting in a denial of service, or possibly execute arbitrary code. Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly implemented address/port checks. A remote attacker could use this issue to perform a cache poisoning attack. Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly implemented query resource name checks. A remote attacker could use this issue to perform a cache poisoning attack. Moshe Kol and Shlomi Oberman discovered that Dnsmasq incorrectly handled multiple query requests for the same resource name. A remote attacker could use this issue to perform a cache poisoning attack. It was discovered that Dnsmasq incorrectly handled memory during DHCP response creation. A remote attacker could possibly use this issue to cause Dnsmasq to consume resources, leading to a denial of service. This issue only affected Ubuntu 16.04 LTS, Ubuntu 18.04 LTS, and Ubuntu 20.04 LTS. Various other issues were also addressed.