Описание
A flaw was found in dnsmasq before version 2.83. 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.
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.
Отчет
Dnsmasq may be run by libvirt and/or NetworkManager. libvirt uses dnsmasq by default to provide DNS service to its guests. NetworkManager may be configured to use dnsmasq to provide DNS service to the system, if a line dns=dnsmasq is present in the [main] section of the configuration file /etc/NetworkManager/NetworkManager.conf.
In Red Hat OpenStack Platform (RHOSP) and Red Hat Virtualization (RHV), the dnsmasq package is provided by the underlying Red Hat Enterprise Linux (RHEL) product. RHOSP and RHV are therefore indirectly affected, so please ensure that the underlying RHEL dnsmasq package is updated.
Меры по смягчению последствий
The impact of this flaw can be reduced by disabling the dnsmasq cache by adding --cache-size=0 when calling dnsmasq or by adding a line with cache-size=0 to the dnsmasq configuration file (/etc/dnsmasq.conf by default).
When using Red Hat Enterprise Linux 8.3 with libvirt through a virt:rhel module, use virsh net-edit <network-name> and reference https://libvirt.org/formatnetwork.html#elementsNamespaces to add the suggested option cache-size=0.
There is no way to customize the dnsmasq configuration generated by libvirt, when using versions of Red Hat Enterprise Linux prior to version 8.3. If dnsmasq is being run through NetworkManager, create a new file in /etc/NetworkManager/dnsmasq.d/ and add cache-size=0 to it.
In all cases, by disabling the cache, you may experience a performance loss in your environment due to all DNS queries being forwarded to the upstream servers. Please evaluate if the mitigation is appropriate for the system’s environment before applying.
Затронутые пакеты
| Платформа | Пакет | Состояние | Рекомендация | Релиз |
|---|---|---|---|---|
| Red Hat Enterprise Linux 5 | dnsmasq | Out of support scope | ||
| Red Hat Enterprise Linux 6 | dnsmasq | Out of support scope | ||
| Red Hat Enterprise Linux 9 | dnsmasq | Not affected | ||
| Red Hat OpenStack Platform 10 (Newton) | dnsmasq | Not affected | ||
| Red Hat OpenStack Platform 13 (Queens) | dnsmasq | Not affected | ||
| Red Hat Enterprise Linux 7 | dnsmasq | Fixed | RHSA-2021:0153 | 19.01.2021 |
| Red Hat Enterprise Linux 7.2 Advanced Update Support | dnsmasq | Fixed | RHSA-2021:0240 | 25.01.2021 |
| Red Hat Enterprise Linux 7.3 Advanced Update Support | dnsmasq | Fixed | RHSA-2021:0245 | 25.01.2021 |
| Red Hat Enterprise Linux 7.4 Advanced Update Support | dnsmasq | Fixed | RHSA-2021:0156 | 19.01.2021 |
| Red Hat Enterprise Linux 7.4 Telco Extended Update Support | dnsmasq | Fixed | RHSA-2021:0156 | 19.01.2021 |
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Дополнительная информация
Статус:
4 Medium
CVSS3
Связанные уязвимости
A flaw was found in dnsmasq before version 2.83. 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.
A flaw was found in dnsmasq before version 2.83. 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.
A flaw was found in dnsmasq before version 2.83. When receiving a quer ...
A flaw was found in dnsmasq before version 2.83. 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.
4 Medium
CVSS3