A recent vulnerability designated as CVE-2024-11187 has been identified in BIND 9, a widely-used Domain Name System (DNS) server. This vulnerability can be exploited by sending specially crafted queries to a server, causing either the authoritative server or an independent resolver to consume disproportionate system resources. This blog post will delve into the details of the vulnerability and provide code snippets and links to original references.

Vulnerability Details

CVE-2024-11187 is a resource consumption vulnerability, which affects BIND 9 versions in the range 9.11. - 9.21.3, as well as their respective security patch releases. Attackers can exploit this vulnerability by constructing a malicious zone that generates responses with many records in the Additional section when querying it. These additional records can cause the server or resolver to use excessive resources, such as CPU and memory, potentially leading to a denial-of-service (DoS) condition.

To exploit this vulnerability, an attacker would need to create a carefully crafted zone file which, when queried, would generate responses with multiple additional records. Here's an example of a zone file designed to exploit this vulnerability:

$TTL 360
@ IN SOA ns.example.com. hostmaster.example.com. (
                            2022010101 ; serial
                            360       ; refresh
                            900        ; retry
                            86400      ; expire
                            360 )     ; minimum

@ IN NS ns.example.com.

resource.example.com. IN A 192.168.1.1
archive.example.com.   IN A 192.168.2.2

_unusual.example.com. 100 IN TXT "This is the crafted record."

*._unusual.example.com. IN TXT "Exploiting CVE-2024-11187."

In the above zone file, we have two normal A records and a wildcard TXT record. When a query is made for any subdomain of "_unusual.example.com", the response will include the wildcard TXT record, padding the Additional section with an extra record. An attacker can send numerous queries for unique subdomains to exploit the vulnerability and consume server resources.

Original References

- ISC Security Advisory
- CVE-2024-11187 Details

Mitigation

It is recommended to update BIND 9 to the most recent security patch release as provided by the maintainers of the software. Patching the vulnerable versions will prevent attackers from exploiting CVE-2024-11187. In addition, server administrators and operators should monitor their DNS infrastructure for unusual query patterns and resource consumption to detect potential exploitation attempts.

Conclusion

CVE-2024-11187 is a severe vulnerability affecting BIND 9 that can be exploited to consume server resources and potentially cause a denial-of-service condition. By constructing malicious zone files and sending specially crafted queries, attackers can exploit this vulnerability. It is crucial for server administrators and operators to update their BIND installations to the latest security patch releases and actively monitor their DNS infrastructure.

Timeline

Published on: 01/29/2025 22:15:28 UTC