CVE-2025-62408
📋 TL;DR
A denial-of-service vulnerability in c-ares resolver library versions 1.32.3 through 1.34.5 causes queries to terminate after maximum attempts when using read_answer() and process_answer() functions. This affects any application or system using vulnerable versions of the c-ares library for DNS resolution.
💻 Affected Systems
- c-ares library
- Applications linking against c-ares
📦 What is this software?
C Ares by C Ares
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption for applications relying on DNS resolution, potentially causing cascading failures in dependent services.
Likely Case
Intermittent DNS resolution failures leading to application timeouts, degraded performance, or partial service unavailability.
If Mitigated
Minimal impact with proper monitoring and failover mechanisms in place, though resolution delays may still occur.
🎯 Exploit Status
Exploitation requires ability to influence DNS responses to trigger the termination condition, which could be achieved through DNS poisoning or controlling upstream DNS servers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.34.6
Vendor Advisory: https://github.com/c-ares/c-ares/security/advisories/GHSA-jq53-42q6-pqr5
Restart Required: Yes
Instructions:
1. Update c-ares to version 1.34.6 or later. 2. Recompile any applications statically linked against c-ares. 3. Restart services using the library.
🔧 Temporary Workarounds
DNS Response Validation
allImplement additional validation of DNS responses at application level to filter potentially malicious responses.
DNS Server Hardening
allSecure upstream DNS servers to prevent response manipulation.
🧯 If You Can't Patch
- Implement DNS query timeouts and retry logic at application level
- Use alternative DNS resolution methods or libraries temporarily
🔍 How to Verify
Check if Vulnerable:
Check c-ares version with: pkg-config --modversion c-ares or check library version in application dependencies.Check Version:
pkg-config --modversion c-aresVerify Fix Applied:
Verify c-ares version is 1.34.6 or higher after update.📡 Detection & Monitoring
Log Indicators:
- Increased DNS query timeouts
- Application errors related to DNS resolution failures
- Unusual termination of DNS resolution processes
Network Indicators:
- Abnormal DNS response patterns
- Repeated DNS queries to same domains
SIEM Query:
source="application_logs" AND ("DNS timeout" OR "resolution failed" OR "c-ares error")