CVE-2015-2686 in Android
Summary
by MITRE
net/socket.c in the Linux kernel 3.19 before 3.19.3 does not validate certain range data for (1) sendto and (2) recvfrom system calls, which allows local users to gain privileges by leveraging a subsystem that uses the copy_from_iter function in the iov_iter interface, as demonstrated by the Bluetooth subsystem.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 09/12/2022
The vulnerability identified as CVE-2015-2686 represents a critical privilege escalation flaw within the Linux kernel's networking subsystem. This issue affects kernel versions 3.19 through 3.19.2 and stems from inadequate validation of range data during socket operations. The flaw specifically impacts the sendto and recvfrom system calls, which are fundamental components of network communication in Unix-like systems. The vulnerability manifests through the iov_iter interface, a critical kernel abstraction that handles input/output operations between user-space and kernel-space buffers. When subsystems such as Bluetooth leverage the copy_from_iter function, they become susceptible to malformed data that bypasses normal validation mechanisms.
The technical exploitation of this vulnerability occurs through a combination of kernel memory management flaws and improper bounds checking. The iov_iter interface is designed to efficiently handle data transfer operations by iterating through memory buffers, but in this case, the range validation fails to properly verify the boundaries of data being copied from user-space to kernel-space. This creates a scenario where malicious local users can craft specially formatted data that appears valid to the system call interface but contains out-of-bounds memory references. The Bluetooth subsystem serves as a particularly effective attack vector because it frequently uses these socket operations for device communication and data transfer, making it a common target for exploitation.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise and data integrity violations. Local users who can execute code on a target system gain the ability to elevate their privileges to root level, effectively bypassing all local security controls. This privilege escalation allows attackers to modify system files, install persistent backdoors, or exfiltrate sensitive information without detection. The vulnerability's exploitation is particularly concerning because it requires minimal privileges to initiate and can be automated through existing kernel interfaces. The flaw demonstrates a classic case of insufficient input validation that allows memory corruption, which aligns with CWE-129 and CWE-787 categories focusing on improper input validation and out-of-bounds reads. From an adversarial perspective, this vulnerability maps directly to ATT&CK technique T1068 which describes the use of local privilege escalation to gain system-level access.
Mitigation strategies for CVE-2015-2686 primarily involve immediate kernel updates to versions 3.19.3 or later, where the range validation has been corrected. System administrators should prioritize patching all affected kernel versions as this vulnerability represents a critical security risk. Additional defensive measures include implementing strict network access controls, monitoring for unusual socket operations, and employing kernel hardening techniques such as stack canaries and address space layout randomization. The vulnerability also highlights the importance of comprehensive input validation in kernel-space code and serves as a reminder that subsystem interfaces like iov_iter require robust boundary checking mechanisms. Organizations should conduct vulnerability assessments to identify systems running affected kernel versions and establish monitoring protocols to detect potential exploitation attempts. The fix implemented in kernel 3.19.3 specifically addresses the validation of range data in the iov_iter interface, ensuring that copy_from_iter operations properly validate memory boundaries before performing data transfers.