Full Report
ISC BIND security advisory (AV26-931)
Analysis Summary
# Vulnerability: Multiple Denial of Service Vulnerabilities in ISC BIND 9
## CVE Details
- **CVE ID:** CVE-2026-XXXXX (Note: The provided advisory AV26-931 refers to a batch of vulnerabilities; specific CVE IDs were not listed in the snippet provided. Please refer to the ISC link for individual IDs).
- **CVSS Score:** 7.5 (Estimated based on typical BIND DoS severity) (High)
- **CWE:** CWE-400 (Uncontrolled Resource Consumption) / CWE-20 (Improper Input Validation)
## Affected Systems
- **Products:** ISC BIND 9 (Standard and Supported Preview Editions)
- **Versions:**
- 9.18.0 through 9.18.50
- 9.18.0-S1 through 9.18.50-S1
- 9.20.0 through 9.20.27
- 9.20.0-S1 through 9.20.27-S1
- 9.21.0 through 9.21.25 (Development Branch)
- **Configurations:** Systems acting as authoritative servers or recursive resolvers. Specific vulnerabilities may depend on features like DNSSEC validation or specific query handling.
## Vulnerability Description
These vulnerabilities typically involve flaws in how BIND 9 processes specific sequences of DNS packets or resource records. In these versions, an attacker can trigger excessive memory consumption or cause the `named` process to terminate unexpectedly (crash) by sending specially crafted DNS queries. This leads to a Denial of Service (DoS) for all users relying on the affected DNS server.
## Exploitation
- **Status:** Not currently reported as exploited in the wild; PoC likely exists internally or for researchers.
- **Complexity:** Low
- **Attack Vector:** Network (Remote)
## Impact
- **Confidentiality:** None
- **Integrity:** None
- **Availability:** High (The primary impact is the crashing of the DNS service).
## Remediation
### Patches
ISC recommends upgrading to the following versions or later:
- **BIND 9.18.51 / 9.18.51-S1**
- **BIND 9.20.28 / 9.20.28-S1**
- **BIND 9.21.26**
### Workarounds
- There are no complete functional workarounds for these vulnerabilities other than upgrading the software.
- Restricting access to the DNS server via ACLs (Access Control Lists) to trusted IP addresses can reduce the attack surface.
## Detection
- **Indicators of Compromise:** Look for `named` process restarts in system logs (`syslog` or `messages`).
- **Detection methods:** Monitor for unusual spikes in memory usage or an influx of malformed DNS packets. Standard IDS/IPS signatures for BIND DoS patterns should be updated.
## References
- **Vendor Advisory:** hxxps[://]kb[.]isc[.]org/docs/aa-00913
- **Cyber Centre Advisory:** hxxps[://]www[.]cyber[.]gc[.]ca/en/alerts-advisories/isc-bind-security-advisory-av26-931