CVE-2018-6555 in Linux
Summary
by MITRE
The irda_setsockopt function in net/irda/af_irda.c and later in drivers/staging/irda/net/af_irda.c in the Linux kernel before 4.17 allows local users to cause a denial of service (ias_object use-after-free and system crash) or possibly have unspecified other impact via an AF_IRDA socket.
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Analysis
by VulDB Data Team • 05/07/2023
The vulnerability identified as CVE-2018-6555 represents a critical use-after-free condition within the Linux kernel's infrared (IrDA) subsystem, specifically affecting the irda_setsockopt function implementation. This flaw exists in the kernel's network stack where IrDA protocol support is implemented through the af_irda.c file, which was originally located in net/irda/ and later relocated to drivers/staging/irda/net/ as part of kernel restructuring efforts. The vulnerability affects all Linux kernel versions prior to 4.17, making it a widespread concern across numerous system deployments that rely on IrDA functionality for wireless communication. The flaw stems from improper memory management during socket option configuration operations, creating a scenario where freed memory locations can be accessed by subsequent operations, leading to unpredictable behavior and system instability.
The technical execution of this vulnerability involves local users exploiting the irda_setsockopt function through AF_IRDA socket operations to trigger a use-after-free condition in the ias_object data structure. When a user manipulates socket options for IrDA communication, the kernel fails to properly validate or manage the lifecycle of ias_object instances, allowing for memory deallocation without proper reference counting or state validation. This particular memory management failure creates a race condition where the kernel may attempt to access memory that has already been freed, causing memory corruption and ultimately leading to system crashes. The vulnerability operates at the kernel level, meaning that successful exploitation bypasses user-space protections and can result in complete system compromise or denial of service conditions that affect the entire operating system.
From an operational impact perspective, this vulnerability creates significant security and stability risks for systems utilizing IrDA functionality, including but not limited to wireless keyboards, mice, printers, and other infrared communication devices. The denial of service aspect can render systems unusable through kernel crashes, while the unspecified other impacts may include privilege escalation opportunities or information disclosure vulnerabilities that could be leveraged by attackers to gain further system access. The vulnerability's local nature means that any user with access to the system can potentially trigger the exploit, making it particularly dangerous in multi-user environments or systems where untrusted users have login access. Network infrastructure devices, embedded systems, and IoT devices that rely on IrDA protocols for communication are especially vulnerable to this type of exploitation.
The remediation approach for CVE-2018-6555 requires immediate kernel version upgrades to 4.17 or later, where the memory management issues have been addressed through proper reference counting and validation of ias_object lifecycle management. System administrators should prioritize patching affected systems, particularly those running older kernel versions that may be exposed to local privilege escalation risks. Additionally, implementing network segmentation and access controls to limit local user access can provide mitigation while patches are deployed. This vulnerability aligns with CWE-416, which describes use-after-free conditions, and represents a typical example of memory safety issues that fall under the ATT&CK technique T1068, involving the exploitation of local privilege escalation vulnerabilities. Organizations should also consider monitoring for unusual kernel crash patterns or system instability that may indicate exploitation attempts, and maintain updated security baselines that include kernel hardening measures and regular security assessments to prevent similar vulnerabilities from emerging in the future.