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CVE-2024-39920

4.3 MEDIUM

📋 TL;DR

SnailLoad is a timing side-channel vulnerability in TCP protocol (RFC 9293) that allows remote attackers to infer content from a client's TCP connections by measuring round-trip times when the client is receiving slow data from an attacker-controlled server. This affects any system using TCP for network communication. The attack requires the victim to connect to both a legitimate service and a malicious server simultaneously.

💻 Affected Systems

Products:
  • All implementations of TCP protocol following RFC 9293
Versions: All versions
Operating Systems: Linux, Windows, macOS, BSD, Unix variants, Embedded systems
Default Config Vulnerable: ⚠️ Yes
Notes: This is a protocol-level vulnerability affecting all TCP implementations. The attack requires the victim to have concurrent connections to both a legitimate service and an attacker-controlled server.

⚠️ Manual Verification Required

This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.

Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).

🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.

Recommended Actions:
  1. Review the CVE details at NVD
  2. Check vendor security advisories for your specific version
  3. Test if the vulnerability is exploitable in your environment
  4. Consider updating to the latest version as a precaution

⚠️ Risk & Real-World Impact

🔴

Worst Case

Attackers could infer sensitive information from encrypted TCP connections, potentially revealing private data, browsing activity, or application state without breaking encryption.

🟠

Likely Case

Limited information leakage about network activity patterns, potentially revealing when specific applications are being used or certain websites are visited.

🟢

If Mitigated

Minimal impact with proper network segmentation, monitoring, and client-side protections against connecting to untrusted servers.

🌐 Internet-Facing: MEDIUM - Attack requires client to connect to attacker-controlled server, but many users may inadvertently connect to malicious servers.
🏢 Internal Only: LOW - Requires attacker to have internal network access and control a server that internal clients connect to.

🎯 Exploit Status

Public PoC: ⚠️ Yes
Weaponized: LIKELY
Unauthenticated Exploit: ⚠️ Yes
Complexity: HIGH

Proof-of-concept code is available on GitHub. Exploitation requires sophisticated timing measurements and control of a server that the victim connects to. The attack is passive and difficult to detect.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: N/A

Vendor Advisory: N/A

Restart Required: No

Instructions:

No official patch available as this is a protocol-level issue. Monitor for TCP stack updates from OS vendors and network equipment manufacturers.

🔧 Temporary Workarounds

Network traffic shaping

linux

Implement traffic shaping to normalize packet timing and reduce timing signal variations

# Use tc on Linux for traffic shaping
tc qdisc add dev eth0 root netem delay 10ms 2ms

Application-layer encryption

all

Use strong application-layer encryption (TLS 1.3) to protect sensitive data even if timing information leaks

🧯 If You Can't Patch

  • Implement strict outbound firewall rules to prevent connections to untrusted servers
  • Use VPNs for all external connections to obscure timing characteristics

🔍 How to Verify

Check if Vulnerable:

All systems using TCP are vulnerable. Check TCP implementation version: 'sysctl net.ipv4.tcp_congestion_control' on Linux or examine network stack version.

Check Version:

uname -a && cat /proc/version (Linux) or systeminfo (Windows)

Verify Fix Applied:

Monitor for OS updates addressing TCP timing side channels. Test with SnailLoad PoC tools if available.

📡 Detection & Monitoring

Log Indicators:

  • Unusual patterns of connections to unknown servers
  • Multiple slow TCP connections from same client

Network Indicators:

  • Unusually consistent RTT measurements
  • Patterns of ACK timing that could indicate measurement

SIEM Query:

source_ip="*" AND dest_port="*" AND bytes_sent<100 AND duration>10s | stats count by source_ip, dest_ip

📊 Metadata

CVE ID: CVE-2024-39920
CVSS v3 Score: 4.3 (MEDIUM)
CVSS Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
CWE: CWE-1255
Published: July 3, 2024
Last Updated: November 21, 2024

🔗 References

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