MB connect line: multiple products partially affected by DNSspooq

Multiple flaws have been found in dnsmasq before version 2.83...

VDE-2021-012 (2021-04-26 13:01 UTC+0200)

Affected Vendors

MB connect line GmbH

Affected Products

Product Affected Version
mbNET/mbNET .rokey <= 6.2.5
mbNET HW1 <= 5.1.10

The products are not affected by the remaining DNSspooq vulnerabilities: CVE-2020-25681,CVE-2020-25682, CVE-2020-25683 and CVE-2020-25687.

Vulnerability Type

Improperly Implemented Security Check for Standard (CWE-358)

Summary

CVE-2020-25684

A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in the forward.c:reply_query() if the reply destination address/port is used by the pending forwarded queries. However, it does not use the address/port to retrieve the exact forwarded query, substantially reducing the number of attempts an attacker on the network would have to perform to forge a reply and get it accepted by dnsmasq. This issue contrasts with RFC5452, which specifies a query's attributes that all must be used to match a reply. This flaw allows an attacker to perform a DNS Cache Poisoning attack. If chained with CVE-2020-25685 or CVE-2020-25686, the attack complexity of a successful attack is reduced. The highest threat from this vulnerability is to data integrity.

CVE-2020-25685

A flaw was found in dnsmasq before version 2.83. When getting a reply from a forwarded query, dnsmasq checks in forward.c:reply_query(), which is the forwarded query that matches the reply, by only using a weak hash of the query name. Due to the weak hash (CRC32 when dnsmasq is compiled without DNSSEC, SHA-1 when it is) this flaw allows an off-path attacker to find several different domains all having the same hash, substantially reducing the number of attempts they would have to perform to forge a reply and get it accepted by dnsmasq. This is in contrast with RFC5452, which specifies that the query name is one of the attributes of a query that must be used to match a reply. This flaw could be abused to perform a DNS Cache Poisoning attack. 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.

CVE-2020-25686

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.

Impact

Please see Summary for details.

Solution

Update to the following versions:

Product Affected Version
mbNET/mbNET .rokey >= 7.0.0
mbNET HW1 >= 5.1.11

Reported by

MB connect line reported this advisory to CERT@VDE.