ZDR Decoding Out-of-Bounds Write in libnfs

Executive Summary

This vulnerability is an out-of-bounds write in the libnfs library version 6.0.2 or earlier. It occurs in three functions (libnfs_zdr_bytes, libnfs_zdr_string, libnfs_zdr_array) that handle ZDR decoding. These functions accept a maxsize parameter to limit data size but fail to enforce it, allowing attackers to write beyond allocated memory buffers by sending specially crafted network messages.

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Detection Guidance

To detect this vulnerability, check if your system uses libnfs version 6.0.2 or earlier. Run 'nfsstat -v' to inspect NFS statistics and verify the installed version with 'dpkg -l libnfs' or 'rpm -qa libnfs'. If vulnerable, update to version 7613236 or later.

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Impact Analysis

An attacker could exploit this to execute arbitrary code, crash applications using libnfs, or gain unauthorized access to system resources. The impact depends on how libnfs is used in your environment, but remote code execution is possible if the library processes untrusted network input.

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Compliance Impact

This vulnerability could lead to data breaches or unauthorized system access, violating confidentiality requirements in GDPR and HIPAA. Organizations using affected libnfs versions may face compliance violations if exploited, potentially resulting in fines or legal penalties.

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Mitigation Strategies

Update libnfs to version 7613236 or later to apply the security fix that enforces maxsize limits in libnfs_zdr_bytes(), libnfs_zdr_string(), and libnfs_zdr_array().

If immediate update is not possible, restrict network access to services using libnfs to trusted sources only.

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