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How the CVE Works
The vulnerability in the `resolv` gem stems from insufficient validation of DNS domain name lengths during decompression. When parsing a malicious DNS packet containing a highly compressed domain name, the library fails to enforce a limit on the decompressed name length. This causes excessive CPU consumption as the resolver recursively processes the oversized name, leading to thread unresponsiveness and a DoS condition. Attackers exploit this by sending crafted DNS responses to applications using vulnerable versions of resolv.
DailyCVE Form
Platform: Ruby (resolv gem)
Version: <0.2.3, 0.4.0-0.6.1, 0.3.0
Vulnerability: DNS decompression DoS
Severity: Moderate
Date: 2025-07-15
Prediction: Patch expected by 2025-07-22
What Undercode Say
Check resolv gem version gem list resolv Example malicious DNS query (simulated) dig @attacker.example.com +compressed malicious.long.domain
How Exploit
- Attacker crafts a DNS response with extreme compression.
2. Victim application queries attacker-controlled DNS.
3. `resolv` decompresses the payload, exhausting CPU.
Protection from this CVE
- Upgrade to `resolv` 0.2.3, 0.3.1, or 0.6.2.
- Implement DNS response size limits.
- Use network-level DNS filtering.
Impact
- Application thread starvation.
- Service disruption via CPU exhaustion.
- Affects Ruby apps using `resolv` for DNS.
Sources:
Reported By: github.com
Extra Source Hub:
Undercode
