A buffer overflow vulnerability was discovered in the way dnsmasq before version 2.83 extract names from DNS packets before validating them with DNSSEC data. An attacker on the network, who can create valid DNS replies, could use this flaw to cause an overflow with arbitrary data in a heap-allocated memory, possibly executing code on the machine. The flaw is in rfc1035.c:extract_name() function, which writes data to the memory pointed by name assuming MAXDNAME*2 bytes are available in the buffer. However, in some code execution paths it is possible extract_name() gets passed an offset from the base buffer, thus reducing in practice the number of available bytes that can be written in the buffer.
A buffer overflow vulnerability was discovered in the way dnsmasq before version 2.83 extract names from DNS packets before validating them with DNSSEC data. An attacker on the network, who can create valid DNS replies, could use this flaw to cause an overflow with arbitrary data in a heap-allocated memory, possibly executing code on the machine. The flaw is in rfc1035.c:extract_name() function, which writes data to the memory pointed by name assuming MAXDNAME*2 bytes are available in the buffer. However, in some code execution paths it is possible extract_name() gets passed an offset from the base buffer, thus reducing in practice the number of available bytes that can be written in the buffer.
https://www.openwall.com/lists/oss-security/2021/01/19/1 https://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2021q1/014599.html https://www.jsof-tech.com/disclosures/dnspooq/ https://thekelleys.org.uk/gitweb/?p=dnsmasq.git;a=commitdiff;h=4e96a4be685c9e4445f6ee79ad0b36b9119b502a
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