CVE-2013-1950 in rpcbind
Summary
by MITRE
The svc_dg_getargs function in libtirpc 0.2.3 and earlier allows remote attackers to cause a denial of service (rpcbind crash) via a Sun RPC request with crafted arguments that trigger a free of an invalid pointer.
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Analysis
by VulDB Data Team • 11/26/2024
The vulnerability identified as CVE-2013-1950 resides within the libtirpc library version 0.2.3 and earlier, specifically within the svc_dg_getargs function that handles Sun RPC requests. This flaw represents a classic buffer over-read condition that occurs when processing malformed RPC arguments, creating a scenario where the system attempts to free memory at an invalid pointer address. The vulnerability manifests when remote attackers craft specific RPC requests designed to exploit the argument parsing logic, leading to a crash of the rpcbind service that manages RPC port mapping. This type of vulnerability falls under the category of improper input validation and memory management issues that are commonly classified as CWE-476, representing a null pointer dereference or improper pointer handling. The impact extends beyond simple service disruption as it can be leveraged to create a persistent denial of service condition against RPC services that rely on the affected library.
The technical exploitation of this vulnerability requires careful crafting of RPC requests that manipulate the svc_dg_getargs function to trigger an invalid memory deallocation. When the function processes the malformed arguments, it follows a code path that leads to attempting to free memory that was either already freed or never allocated, resulting in a segmentation fault that terminates the rpcbind process. This behavior aligns with the ATT&CK technique T1499.004, which involves network denial of service attacks targeting services and protocols. The vulnerability's exploitation does not require elevated privileges and can be executed remotely, making it particularly dangerous in networked environments where RPC services are exposed to untrusted networks. The flaw demonstrates a fundamental weakness in the library's argument parsing mechanism where insufficient validation occurs before memory operations are performed.
The operational impact of CVE-2013-1950 extends beyond immediate service disruption to create broader security implications for systems relying on RPC services. When rpcbind crashes, it affects the availability of all RPC services that depend on port mapping, potentially disrupting critical network services such as NFS, NIS, and other distributed computing services. This vulnerability can be particularly damaging in enterprise environments where RPC-based services form the backbone of distributed applications and file sharing systems. The crash of rpcbind creates a cascading effect where dependent services become unavailable, leading to potential data access issues and operational downtime. Organizations may experience significant service interruptions as the rpcbind service restarts and re-establishes port mappings, which can take considerable time depending on system configuration and network complexity. The vulnerability also represents a potential vector for reconnaissance activities, as attackers can use it to identify systems running vulnerable versions of libtirpc and potentially map out network service configurations.
Mitigation strategies for CVE-2013-1950 primarily involve upgrading to libtirpc version 0.2.4 or later, where the memory management issues in svc_dg_getargs have been addressed through proper input validation and pointer handling. System administrators should implement network segmentation to limit exposure of RPC services to untrusted networks and consider disabling unnecessary RPC services to reduce the attack surface. The vulnerability's remediation aligns with the principle of least privilege and defense in depth strategies, as outlined in cybersecurity frameworks such as NIST SP 800-53. Additional mitigations include implementing network access controls to restrict RPC traffic to trusted sources and deploying intrusion detection systems to monitor for suspicious RPC activity patterns. Organizations should also conduct regular vulnerability assessments to identify systems running older versions of libtirpc and ensure timely patch deployment. The fix implemented in newer versions typically involves adding proper bounds checking and null pointer validation before memory deallocation operations, directly addressing the memory safety issues that led to the crash condition.