CVE-2022-38177: ISC BIND DOS Vulnerability

CVE-2022-38177 Overview

CVE-2022-38177 is a memory leak vulnerability affecting ISC BIND DNS server software. By spoofing the target resolver with responses that contain a malformed ECDSA signature, an attacker can trigger a small memory leak. Through sustained exploitation, it is possible to gradually erode available memory to the point where the named daemon crashes due to resource exhaustion.

Critical Impact

Remote attackers can cause denial of service by exhausting memory resources on DNS resolvers through continuous delivery of malformed ECDSA signatures, eventually crashing the BIND service.

Affected Products

• ISC BIND (multiple versions including 9.9.x through 9.16.x)
• Debian Linux 10.0 and 11.0
• Fedora 35, 36, and 37
• NetApp Active IQ Unified Manager for VMware vSphere

Discovery Timeline

• 2022-09-21 - CVE-2022-38177 published to NVD
• 2025-05-28 - Last updated in NVD database

Technical Details for CVE-2022-38177

Vulnerability Analysis

This vulnerability (CWE-401: Missing Release of Memory after Effective Lifetime) resides in the DNSSEC signature validation code within ISC BIND. When the DNS resolver processes a response containing a malformed ECDSA signature, the memory allocated for processing the signature is not properly released. While each individual leak is small, an attacker can repeatedly send malformed responses to gradually deplete the available memory pool.

The attack is particularly concerning because it can be conducted remotely without any authentication. An attacker simply needs to be able to send spoofed DNS responses to the target resolver, which is feasible in many network configurations. The vulnerability specifically affects DNSSEC-validating resolvers when processing ECDSA signatures.

Root Cause

The root cause is improper memory management in the ECDSA signature validation routine. When an ECDSA signature fails validation due to malformation, the code path that handles the error does not correctly free all allocated memory buffers. This results in a memory leak that accumulates over time with each malformed signature processed.

Attack Vector

The attack exploits the network-accessible DNS service by sending spoofed DNS responses with intentionally malformed ECDSA signatures. The attacker does not require any privileges or user interaction to exploit this vulnerability.

An attacker targeting a BIND resolver would:

1. Identify a target DNSSEC-validating resolver running a vulnerable version of BIND
2. Craft DNS responses containing malformed ECDSA signatures
3. Spoof these responses to appear as legitimate answers to DNS queries the resolver makes
4. Continuously send malformed responses to gradually exhaust memory
5. Eventually cause the named process to crash when memory is exhausted

The attack can be sustained over time to maintain the denial of service condition.

Detection Methods for CVE-2022-38177

Indicators of Compromise

• Gradual increase in memory consumption by the named process over time
• Unexpected crashes or restarts of the BIND DNS service with out-of-memory errors
• Log entries indicating DNSSEC validation failures for ECDSA signatures
• Unusual volume of DNS responses containing ECDSA signatures from suspicious sources

Detection Strategies

• Monitor the named process memory usage for abnormal growth patterns using tools like top, ps, or dedicated monitoring solutions
• Implement SIEM rules to alert on BIND service crashes accompanied by memory exhaustion indicators
• Deploy network-level monitoring to detect anomalous DNS response traffic volumes or spoofed responses
• Review BIND logs for repeated DNSSEC validation failures that could indicate exploitation attempts

Monitoring Recommendations

• Configure memory usage alerts for the BIND named process with appropriate thresholds
• Implement automated service health checks to detect and respond to BIND service failures
• Enable detailed DNSSEC logging to capture signature validation errors for forensic analysis
• Deploy DNS query logging to correlate suspicious responses with potential attack sources

How to Mitigate CVE-2022-38177

Immediate Actions Required

• Update ISC BIND to the latest patched version as recommended by ISC
• Review and apply security updates from your Linux distribution (Debian, Fedora, etc.)
• Monitor DNS servers for signs of memory exhaustion or service instability
• Consider implementing rate limiting on DNS responses to reduce attack surface

Patch Information

ISC has released patches addressing this vulnerability. Administrators should consult the ISC Knowledge Base CVE-2022-38177 for specific version information and download links. Distribution-specific patches are also available:

• Debian: Debian Security Advisory DSA-5235
• Fedora: Updates available through Fedora package repositories
• Gentoo: Gentoo GLSA 202210-25
• NetApp: NetApp Security Advisory NTAP-20221228-0010

Workarounds

• If patching is not immediately possible, consider temporarily disabling DNSSEC validation (note: this reduces security)
• Implement network-level filtering to block suspicious DNS response traffic from untrusted sources
• Configure resource limits for the named process to prevent complete system exhaustion
• Deploy redundant DNS infrastructure to maintain availability if one server is affected

# Check current BIND version
named -v

# Monitor named process memory usage
ps aux | grep named
watch -n 60 'ps -o pid,user,%mem,rss,vsz,comm -p $(pgrep named)'

# Check for available updates (Debian/Ubuntu)
apt update && apt list --upgradable | grep bind

# Check for available updates (RHEL/Fedora)
dnf check-update bind