CVE-2022-35409
📋 TL;DR
This vulnerability in Mbed TLS allows unauthenticated attackers to send specially crafted DTLS ClientHello messages to servers with specific configurations, causing heap buffer over-reads of up to 255 bytes. This can lead to server crashes or potential information disclosure through error responses. Systems are affected if they use Mbed TLS with DTLS client port reuse enabled and insufficient buffer sizes.
💻 Affected Systems
- Mbed TLS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Server crash leading to denial of service, or information disclosure of up to 255 bytes of heap memory through error responses, potentially exposing sensitive data.
Likely Case
Server crash causing denial of service, disrupting DTLS services and affecting availability.
If Mitigated
No impact if vulnerable configurations are disabled or patches are applied.
🎯 Exploit Status
Exploitation requires sending malformed DTLS packets to vulnerable servers with specific configurations.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Mbed TLS 2.28.1 or 3.2.0
Vendor Advisory: https://mbed-tls.readthedocs.io/en/latest/security-advisories/advisories/mbedtls-security-advisory-2022-07.html
Restart Required: Yes
Instructions:
1. Update Mbed TLS to version 2.28.1 or 3.2.0. 2. Recompile applications using Mbed TLS. 3. Restart affected services.
🔧 Temporary Workarounds
Disable DTLS client port reuse
allDisable MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE in configuration to prevent exploitation.
# In mbedtls_config.h or build configuration, set MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE to 0
Increase buffer size
allEnsure MBEDTLS_SSL_IN_CONTENT_LEN is set to at least 258 bytes (or 571 if using custom cookie check).
# In mbedtls_config.h, set MBEDTLS_SSL_IN_CONTENT_LEN to 258 or higher
🧯 If You Can't Patch
- Disable DTLS services if not required
- Implement network filtering to block DTLS traffic from untrusted sources
🔍 How to Verify
Check if Vulnerable:
Check Mbed TLS version and configuration: verify if version is below 2.28.1 or 3.2.0, and if MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE is enabled with insufficient MBEDTLS_SSL_IN_CONTENT_LEN.Check Version:
# For applications using Mbed TLS, check version in source or via mbedtls_version_get_string()Verify Fix Applied:
Confirm Mbed TLS version is 2.28.1 or higher for 2.x branch, or 3.2.0 or higher for 3.x branch.📡 Detection & Monitoring
Log Indicators:
- DTLS connection errors, server crashes, or abnormal termination logs
Network Indicators:
- Malformed DTLS ClientHello packets with unusual sizes
SIEM Query:
Search for DTLS protocol errors or server crash events in application logs🔗 References
- https://github.com/Mbed-TLS/mbedtls/releases
- https://lists.debian.org/debian-lts-announce/2022/12/msg00036.html
- https://mbed-tls.readthedocs.io/en/latest/security-advisories/advisories/mbedtls-security-advisory-2022-07.html
- https://github.com/Mbed-TLS/mbedtls/releases
- https://lists.debian.org/debian-lts-announce/2022/12/msg00036.html
- https://mbed-tls.readthedocs.io/en/latest/security-advisories/advisories/mbedtls-security-advisory-2022-07.html
