CVE-2015-5986 in BIND
Summary
by MITRE
openpgpkey_61.c in named in ISC BIND 9.9.7 before 9.9.7-P3 and 9.10.x before 9.10.2-P4 allows remote attackers to cause a denial of service (REQUIRE assertion failure and daemon exit) via a crafted DNS response.
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Analysis
by VulDB Data Team • 06/14/2022
The vulnerability identified as CVE-2015-5986 represents a critical denial of service flaw affecting the Internet Systems Consortium BIND DNS server software. This issue specifically impacts versions 9.9.7 prior to 9.9.7-P3 and 9.10.x prior to 9.10.2-P4, where the named daemon becomes susceptible to remote exploitation through malformed DNS response packets. The vulnerability manifests in the openpgpkey_61.c source file, which handles OpenPGP key record processing within the DNS resolver functionality. When a malicious actor crafts a specially formatted DNS response containing invalid OpenPGP key data, the BIND server's assertion mechanism triggers an unrecoverable failure that results in the daemon crashing and terminating its operation. This behavior directly violates the fundamental availability principles of network services and represents a classic example of a resource exhaustion attack vector that can be exploited without authentication or privileged access. The vulnerability falls under CWE-119, which describes weaknesses in memory handling that can lead to assertion failures and system instability.
The technical exploitation of this vulnerability relies on the improper validation of DNS response data during OpenPGP key record processing within the BIND resolver. When the named daemon receives a DNS response containing malformed OpenPGP key data, the assertion checking mechanism in openpgpkey_61.c fails to properly handle the invalid input, causing an assertion failure that terminates the daemon process. This type of assertion failure represents a fundamental software design flaw where insufficient input validation leads to unhandled exceptions that crash the entire service. The attack vector operates entirely over the network without requiring any authentication credentials, making it particularly dangerous in production environments where DNS servers serve as critical infrastructure components. From an operational standpoint, this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks that target DNS services and can effectively disrupt critical network infrastructure. The flaw demonstrates poor error handling practices in the DNS resolution stack, where malformed input should be gracefully rejected rather than causing complete service termination.
The operational impact of CVE-2015-5986 extends beyond simple service disruption to potentially compromise entire network infrastructures that depend on BIND DNS servers for name resolution. When the named daemon crashes and exits, all DNS resolution services provided by that server become unavailable until manual intervention or automatic restart occurs, creating cascading failures that can affect numerous dependent services and applications. Organizations relying on BIND for critical DNS operations face significant risk of service degradation or complete outages when this vulnerability is exploited. The vulnerability's remote nature means that attackers can exploit it from anywhere on the internet without requiring physical access to the network, making it particularly dangerous for publicly accessible DNS servers. The crash condition also creates potential for amplification attacks where multiple vulnerable servers can be simultaneously targeted to maximize the impact of the denial of service. This vulnerability underscores the critical importance of proper input validation and error handling in network services, as even malformed DNS responses should not cause complete daemon termination. Organizations should implement comprehensive monitoring for DNS service availability and ensure that all BIND installations are updated to patched versions to prevent exploitation of this vulnerability. The remediation process requires careful attention to version compatibility and testing of updated configurations to ensure that DNS resolution services continue to function properly after applying the security patches.