Out-of-Bounds Read in FreeRDP Smartcard Handling

Executive Summary

This is an out-of-bounds read vulnerability in FreeRDP versions from 2.0.0-beta1 to 3.27.1. It occurs in the smartcard_LocateCardsByATRA_Call function where the cbAtr byte count is not capped. Malicious RDP servers can send crafted ATR mask arrays to exploit query timing as an oracle, leaking heap memory bit-by-bit to defeat ASLR and aid RCE exploits.

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Detection Guidance

Check FreeRDP version with 'xfreerdp --version' or 'apt show freerdp2-x11' (Debian/Ubuntu). Affected versions are from 2.0.0-beta1 to 3.27.1. Monitor network traffic for malformed ATR mask arrays sent to RDP ports. Use 'tcpdump -i any -w freerdp_traffic.pcap port 3389' to capture suspicious packets.

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Impact Analysis

An attacker could exploit this to leak sensitive memory contents, bypass ASLR protections, and potentially chain with other vulnerabilities to achieve remote code execution. This could lead to unauthorized access, data theft, or system compromise if FreeRDP is used to connect to untrusted RDP servers.

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Compliance Impact

This vulnerability could lead to unauthorized data access or disclosure, violating confidentiality requirements in GDPR and HIPAA. Organizations using vulnerable FreeRDP versions may face compliance violations if exploited, potentially resulting in legal penalties or reputational damage.

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Mitigation Strategies

Upgrade FreeRDP to version 3.28.0 or later immediately. Disable smartcard redirection if not needed by setting 'smartcard' to 'false' in RDP client configurations. Block external RDP access via firewalls until patched. Monitor systems for unusual memory access patterns or ASLR bypass attempts.

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