CVE-2013-3076 in Linux
Summary
by MITRE
The crypto API in the Linux kernel through 3.9-rc8 does not initialize certain length variables, which allows local users to obtain sensitive information from kernel stack memory via a crafted recvmsg or recvfrom system call, related to the hash_recvmsg function in crypto/algif_hash.c and the skcipher_recvmsg function in crypto/algif_skcipher.c.
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Analysis
by VulDB Data Team • 05/10/2021
The vulnerability described in CVE-2013-3076 represents a critical information disclosure flaw within the Linux kernel's cryptographic API subsystem. This issue affects kernel versions through 3.9-rc8 and stems from improper initialization of length variables within the crypto API implementation. The vulnerability specifically targets two key functions: hash_recvmsg in crypto/algif_hash.c and skcipher_recvmsg in crypto/algif_skcipher.c, which are responsible for handling cryptographic operations through the AF_ALG socket interface. These functions process recvmsg and recvfrom system calls that allow userspace applications to interact with kernel cryptographic algorithms, creating an attack surface where malicious code can exploit uninitialized memory contents.
The technical flaw manifests when local attackers craft specially designed recvmsg or recvfrom system calls that trigger the affected cryptographic functions without proper initialization of length parameters. This uninitialized state causes the kernel to return sensitive data from stack memory that may contain previously used variables, cryptographic keys, or other confidential information. The vulnerability is classified under CWE-1288, which deals with uninitialized variables in cryptographic contexts, and aligns with ATT&CK technique T1005 for data from local system. The flaw is particularly dangerous because it operates at the kernel level, allowing attackers to extract information that could compromise the security of cryptographic operations and potentially reveal system secrets.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to gather sensitive cryptographic material that might be used to break encryption, impersonate systems, or compromise the integrity of cryptographic protocols. Local users who can execute crafted system calls gain access to kernel stack memory contents that may include session keys, cryptographic parameters, or other confidential data that should remain protected. This vulnerability undermines the fundamental security assumptions of the kernel's cryptographic subsystem and can be exploited to weaken the overall security posture of affected systems. The attack requires local privileges but does not need elevated permissions, making it particularly concerning for environments where untrusted users might have access to system resources.
Mitigation strategies for CVE-2013-3076 focus on patching the kernel to properly initialize the affected length variables in both hash_recvmsg and skcipher_recvmsg functions. System administrators should immediately apply the relevant kernel updates that address this vulnerability, as the fix involves ensuring that all length parameters are properly initialized before use in cryptographic operations. Organizations should also implement monitoring for suspicious recvmsg and recvfrom system calls that might indicate exploitation attempts, particularly when these calls are made through AF_ALG sockets. The fix aligns with security best practices outlined in the Common Vulnerability Scoring System and represents a fundamental requirement for maintaining the integrity of kernel cryptographic APIs. Additionally, system hardening measures such as restricting access to AF_ALG sockets and implementing proper privilege controls can provide additional defense-in-depth layers against potential exploitation attempts.