CVE-2023-31137 Information

Description

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.

Reference

https://github.com/samboy/MaraDNS/security/advisories/GHSA-58m7-826v-9c3c https://github.com/samboy/MaraDNS/commit/bab062bde40b2ae8a91eecd522e84d8b993bab58 https://github.com/samboy/MaraDNS/blob/08b21ea20d80cedcb74aa8f14979ec7c61846663/dns/Decompress.c#L886