HIGH Vulnerabilities #Denial of Service #CISA KEV

CVE-2015-5477: Remote DoS in ISC BIND via TKEY Queries

2026-10-08 21:00 UTC 3 min read Runtime Rebel Intel

Primary source: cisa.gov

This article was written by a language model from the source above and was not reviewed by a human before publication. Verify anything operational against the original. Editorial policy

Key points

Immediate impact: Remote Denial of Service attacks target ISC BIND, affecting critical DNS services globally due to confirmed active exploitation.
Affected systems: Specifically, ISC BIND installations are vulnerable to data processing errors through crafted TKEY queries.
Remediation: Prioritize applying vendor mitigations and ensure compliance with CISA BOD 26-04 to address this threat immediately.

Urgent Advisory: CISA Confirms Active Exploitation of ISC BIND DoS Vulnerability (CVE-2015-5477)

Runtime Rebel is issuing an urgent advisory regarding CVE-2015-5477, a critical Denial of Service (DoS) vulnerability impacting ISC BIND, the widely deployed Domain Name System (DNS) software. The Cybersecurity and Infrastructure Security Agency (CISA) has added this vulnerability to its Known Exploited Vulnerabilities Catalog, confirming active exploitation in the wild. This confirmation elevates the risk associated with this flaw, necessitating immediate attention from all organizations utilizing ISC BIND for their DNS infrastructure.

DNS is a foundational service for nearly all internet communications, translating human-readable domain names into IP addresses. A successful DoS attack against DNS infrastructure can render services inaccessible, disrupting business operations, communications, and critical online functions. The confirmed in-the-wild exploitation of CVE-2015-5477 means that adversaries are actively leveraging this flaw, posing a direct and immediate threat to affected systems.

Technical Details and Analysis of ISC BIND TKEY Query Exploitation

The vulnerability, identified as CVE-2015-5477, stems from data processing errors within ISC BIND that can be triggered by specially crafted TKEY queries. TKEY queries are part of the Transaction Key (TSIG) mechanism in DNS, used for cryptographic authentication and authorization. Malicious actors can exploit these processing errors to cause the BIND daemon to crash, leading to a Denial of Service for DNS resolution services. This aligns with the CWE-19 weakness, which refers to data processing errors that can lead to crashes or other undesirable outcomes.

The ability of a remote attacker to trigger this DoS without authentication makes this vulnerability particularly severe. Organizations running vulnerable versions of ISC BIND are exposed to potential widespread service outages if their DNS servers are targeted. Understanding ISC BIND TKEY query exploitation is crucial for security teams to identify the attack vector and implement effective countermeasures. The fact that CISA has mandated remediation for federal agencies underscores the significant operational impact and security risk this vulnerability presents.

Defending Against ISC BIND CVE-2015-5477 DoS Attacks

Given the confirmed active exploitation, immediate action is paramount for all organizations managing ISC BIND deployments. The primary recommendation is to apply mitigations in accordance with vendor instructions. While the original vendor guidance would typically involve patching, organizations should also review their existing security posture related to DNS services.

Key steps for mitigating ISC BIND Denial of Service attacks include:

Apply Vendor Mitigations: Prioritize and implement all available patches or configuration changes provided by ISC BIND to address CVE-2015-5477. Refer to official ISC advisories for specific guidance.
Comply with CISA BOD 26-04: Adhere to CISA’s Binding Operational Directive (BOD) 26-04, which mandates federal agencies prioritize security updates based on risk. This directive also provides guidance for cloud services and requires evaluating each asset’s internet exposure.
Assess Internet Exposure: Critically evaluate the internet exposure of all ISC BIND instances. Reduce direct exposure where possible, perhaps by placing DNS resolvers behind protective measures or limiting query sources to trusted networks.
Consider Discontinuation: If effective mitigations are unavailable or cannot be immediately applied, organizations should consider discontinuing the use of the affected product until a secure resolution is in place.
Monitor and Incident Response: Implement continuous monitoring for unusual DNS traffic patterns, particularly those involving TKEY queries, which could indicate attempts to exploit CVE-2015-5477. Ensure your incident response plan includes procedures for addressing DNS service disruptions.

The federal remediation due date for this vulnerability is 2026-10-11. Organizations, especially those supporting critical infrastructure, should not delay in addressing this actively exploited flaw.

#Denial of Service #CISA KEV

X/Twitter LinkedIn Reddit HN

← Back to Articles