MaraDNS is open-source software that implements the Domain Name System (DNS). In version 3.5.0024 and prior, a remotely exploitable integer underflow vulnerability in the DNS packet decompression function allows an attacker to cause a Denial of Service by triggering an abnormal program termination. The vulnerability exists in the `decomp_get_rddata` function within the `Decompress.c` file. When handling a DNS packet with an Answer RR of qtype 16 (TXT record) and any qclass, if the `rdlength` is smaller than `rdata`, the result of the line `Decompress.c:886` is a negative number `len = rdlength - total;`. This value is then passed to the `decomp_append_bytes` function without proper validation, causing the program to attempt to allocate a massive chunk of memory that is impossible to allocate. Consequently, the program exits with an error code of 64, causing a Denial of Service. One proposed fix for this vulnerability is to patch `Decompress.c:887` by breaking `if(len <= 0)`, which has been incorporated in version 3.5.0036 via commit bab062bde40b2ae8a91eecd522e84d8b993bab58.

An issue was discovered in MaraDNS Deadwood through 3.5.0021 that allows variant V1 of unintended domain name resolution. A revoked domain name can still be resolvable for a long time, including expired domains and taken-down malicious domains. The effects of an exploit would be widespread and highly impactful, because the exploitation conforms to de facto DNS specifications and operational practices, and overcomes current mitigation patches for "Ghost" domain names.

The resolver in MaraDNS before 1.3.0.7.15 and 1.4.x before 1.4.12 overwrites cached server names and TTL values in NS records during the processing of a response to an A record query, which allows remote attackers to trigger continued resolvability of revoked domain names via a "ghost domain names" attack.

The authoritative server in MaraDNS through 2.0.04 computes hash values for DNS data without restricting the ability to trigger hash collisions predictably, which might allow local users to cause a denial of service (CPU consumption) via crafted records in zone files, a different vulnerability than CVE-2012-0024.