CVE-2019-15923 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel before 5.0.9. There is a NULL pointer dereference for a cd data structure if alloc_disk fails in drivers/block/paride/pf.c.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability identified as CVE-2019-15923 represents a critical NULL pointer dereference flaw within the Linux kernel's parallel port interface subsystem. This issue specifically affects systems running kernel versions prior to 5.0.9 and resides in the paride/pf.c driver file responsible for handling parallel port devices. The flaw manifests when the alloc_disk function fails during device initialization, leaving a cd data structure uninitialized while subsequent code attempts to dereference it. This condition creates a potential system crash or denial of service scenario that could be exploited by malicious actors to disrupt system operations.
The technical implementation of this vulnerability stems from inadequate error handling within the parallel port driver's initialization sequence. When alloc_disk fails to allocate necessary disk resources, the code path does not properly validate that the cd data structure has been successfully initialized before proceeding with operations that assume its validity. This represents a classic null pointer dereference pattern that falls under CWE-476 which specifically addresses NULL pointer dereferences in software implementations. The flaw demonstrates poor defensive programming practices where error conditions are not adequately checked before proceeding with subsequent operations that depend on previously allocated resources.
From an operational perspective, this vulnerability presents significant risks to systems relying on parallel port functionality, particularly in enterprise environments where such interfaces may still be in use for legacy devices or specialized hardware. The impact extends beyond simple system crashes to potentially enable privilege escalation or denial of service attacks that could affect critical infrastructure operations. Attackers could exploit this weakness to cause system instability, particularly in environments where parallel port devices are actively utilized or where the kernel module is loaded automatically during system boot processes. The vulnerability's exploitation potential is enhanced by the fact that it occurs during normal device initialization, making it difficult to detect and prevent through standard runtime monitoring.
Mitigation strategies for CVE-2019-15923 primarily focus on immediate kernel version upgrades to 5.0.9 or later where the fix has been implemented. System administrators should prioritize patching affected systems, particularly those running older kernel versions or those that have not received security updates. Additionally, implementing runtime monitoring to detect unusual kernel behavior or system crashes can help identify potential exploitation attempts. Organizations should also consider disabling unused parallel port interfaces through kernel module blacklisting or hardware-level disconnection to reduce the attack surface. The fix implemented in the patched kernel version addresses the root cause by ensuring proper error handling and validation of allocated resources before proceeding with operations that depend on those resources, aligning with ATT&CK technique T1068 which addresses privilege escalation through kernel vulnerabilities.