Bypassing Zero-Trust Policies to Exploit Vulnerabilities & Manipulate NHI Secrets

A comprehensive security research demonstration has revealed how attackers can systematically undermine modern zero-trust security frameworks by exploiting a critical DNS vulnerability to disrupt automated secret rotation mechanisms.

The research showcases a sophisticated attack chain that begins with crashing DNS servers and culminates in unauthorized access to protected cloud services, highlighting significant weaknesses in current Non-Human Identity (NHI) management practices.

The demonstration centers on CVE-2025-40775, a recently disclosed denial-of-service vulnerability affecting BIND DNS servers versions 9.20.0 through 9.20.8.

This flaw allows remote attackers to crash DNS servers by sending malformed Transaction Signature (TSIG) packets containing invalid algorithm field values, causing immediate assertion failures and service termination.

The vulnerability carries a CVSS score of 7.5 and requires no authentication, making it particularly dangerous for internet-facing DNS infrastructure.

Security researcher AlexSvobo identified this critical attack vector and developed a proof-of-concept demonstration that illustrates how DNS infrastructure failures can cascade into complete zero-trust policy bypasses.

The research project, published as an open-source repository, provides a controlled cloud-native laboratory environment that simulates real-world enterprise security architectures including secrets managers, API services, and automated NHI rotation systems.

The attack methodology follows a three-phase approach that exploits the interconnected nature of modern cloud security controls.

Initially, attackers craft malicious DNS packets using tools like Scapy to trigger the BIND vulnerability, causing DNS server crashes and widespread resolution failures.

Subsequently, this DNS disruption prevents NHI clients from communicating with secrets management services, forcing systems to rely on static fallback credentials or break-glass authentication mechanisms that are often less secure than dynamic secrets.

DNS Exploitation and Infrastructure Disruption Mechanics

The technical implementation of the DNS attack demonstrates the vulnerability’s severity through precise packet manipulation targeting TSIG record validation.

The exploit code reveals how attackers can construct DNS queries with deliberately malformed TSIG signatures that bypass initial validation checks but trigger fatal assertion failures during processing.

The demonstration shows the exploit packet containing a crafted TSIG resource record with an invalid algorithm identifier “invalid-algo-id-255.example.com” which causes BIND to crash with exit code 139.

Log analysis reveals the critical assertion failure occurring at dns_message_reply function, with the error message “REQUIRE (((name) != ((void *)0) && ((const isc_magic_t *) (name))->magic == (((‘D’) << 24 | (‘N’) << 16 | (‘S’) << 8 | (‘n’))))) failed”.

When NHI clients attempt secret rotation, they encounter repeated connection failures with “getaddrinfo failed” errors, forcing degradation to static credentials like “STATIC_BREAK_GLASS_KEY_XYZABC” that subsequently enable unauthorized API access with responses indicating “Access granted with static API key!”.

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