CVE-2023-35784 – This vulnerability in OpenBSD and LibreSSL allo... (How to Fix)

Q: What is the severity of CVE-2023-35784?

CVE-2023-35784 has a CVSS score of 9.8 (CRITICAL). This vulnerability in OpenBSD and LibreSSL allows memory corruption through double-free or use-after-free conditions in SSL_clear function. Attackers could potentially execute arbitrary code or cause denial of service. Only OpenBSD and LibreSSL installations are affected; OpenSSL is not vulnerable.

📋 TL;DR

This vulnerability in OpenBSD and LibreSSL allows memory corruption through double-free or use-after-free conditions in SSL_clear function. Attackers could potentially execute arbitrary code or cause denial of service. Only OpenBSD and LibreSSL installations are affected; OpenSSL is not vulnerable.

💻 Affected Systems

Products:

OpenBSD
LibreSSL

Versions: OpenBSD 7.2 before errata 026, OpenBSD 7.3 before errata 004, LibreSSL before 3.6.3, LibreSSL 3.7.x before 3.7.3

Operating Systems: OpenBSD

Default Config Vulnerable: ⚠️ Yes

Notes: Any system using affected LibreSSL versions or running affected OpenBSD versions with SSL/TLS services enabled

📦 What is this software?

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution leading to complete system compromise, data theft, or persistent backdoor installation

🟠

Likely Case

Denial of service causing SSL/TLS service crashes and service disruption

🟢

If Mitigated

Limited impact with proper network segmentation and minimal exposure

🌐 Internet-Facing: HIGH

🏢 Internal Only: MEDIUM

🎯 Exploit Status

Public PoC: ✅ No

Weaponized: UNKNOWN

Unauthenticated Exploit: ⚠️ Yes

Complexity: MEDIUM

Memory corruption vulnerabilities in SSL/TLS libraries are frequently targeted due to their critical network exposure

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: OpenBSD 7.2 errata 026, OpenBSD 7.3 errata 004, LibreSSL 3.6.3, LibreSSL 3.7.3

Vendor Advisory: https://ftp.openbsd.org/pub/OpenBSD/LibreSSL/libressl-3.6.3-relnotes.txt

Restart Required: Yes

Instructions:

1. Apply OpenBSD patches: syspatch for 7.2 or 7.3. 2. Update LibreSSL: pkg_add -u libressl. 3. Restart affected SSL/TLS services. 4. Reboot system if kernel components affected.

🔧 Temporary Workarounds

Disable vulnerable SSL/TLS services

all

Temporarily disable SSL/TLS services using affected libraries until patching

systemctl stop [service-name]
rcctl stop [service-name]

🧯 If You Can't Patch

Implement strict network segmentation to isolate vulnerable systems
Deploy web application firewall with SSL/TLS inspection capabilities

🔍 How to Verify

Check if Vulnerable:

Check OpenBSD version: uname -a. Check LibreSSL version: openssl version. Compare against affected versions.

Check Version:

openssl version

Verify Fix Applied:

Verify patch applied: syspatch -l shows 026_ssl or 004_ssl. Confirm LibreSSL version >= 3.6.3 or >= 3.7.3.

📡 Detection & Monitoring

Log Indicators:

SSL/TLS service crashes
Memory corruption errors in system logs
Unexpected process termination

Network Indicators:

Abnormal SSL/TLS handshake failures
Connection resets during SSL negotiation

SIEM Query:

source="system_logs" AND ("SSL_clear" OR "libressl" OR "openssl") AND ("crash" OR "segfault" OR "memory")

📊 Metadata

CVE ID: CVE-2023-35784

CVSS v3 Score: 9.8 (CRITICAL)

CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CWE: CWE-415

Published: June 16, 2023

Last Updated: November 21, 2024

🔗 References

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