CVE-2026-64101 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
fwctl: pds: Validate RPC input size before parsing
The fwctl core allocates the device-specific RPC input buffer with fwctl_rpc.in_len and passes that buffer to the driver callback.
pdsfc_fw_rpc() casts the buffer to struct fwctl_rpc_pds and then calls pdsfc_validate_rpc(), which reads fields from that structure before checking that the input buffer is large enough to contain it. A short in_len can make pds_fwctl read beyond the allocation.
Reject pds RPC buffers that are smaller than struct fwctl_rpc_pds before parsing any pds-specific fields.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability resides within the Linux kernel's firewall control mechanism, specifically affecting the fwctl framework's handling of device-specific RPC (Remote Procedure Call) operations. This issue impacts the pds (Packet Data Service) subsystem where the fwctl core component manages allocation and processing of RPC input buffers. The flaw manifests in how the system validates buffer sizes before parsing structured data, creating a potential for out-of-bounds memory access that could be exploited by malicious actors.
The technical implementation involves the fwctl_rpc.in_len parameter which determines the size of the allocated buffer for device-specific RPC operations. When the pdsfc_fw_rpc() function processes these buffers, it immediately casts the buffer to a struct fwctl_rpc_pds type and invokes pdsfc_validate_rpc(). However, this validation process occurs after the casting operation, meaning that fields within the structure are read before confirming that sufficient buffer space exists to contain the entire structure. This sequence creates a classic buffer over-read condition where the system attempts to access memory locations beyond the allocated buffer boundaries.
The operational impact of this vulnerability extends across multiple attack vectors within the kernel's network security framework. An attacker could potentially craft malicious RPC input with intentionally small in_len values to trigger the out-of-bounds read condition, leading to information disclosure, system instability, or privilege escalation opportunities. The flaw aligns with CWE-129 Input Validation and CWE-787 Out-of-bounds Write categories, representing a critical security weakness in kernel space memory management that could compromise system integrity. This vulnerability particularly affects systems utilizing fwctl for network packet filtering and firewall operations, where the pds subsystem handles specialized RPC communications.
Mitigation strategies should focus on implementing early buffer size validation before any parsing operations occur. The recommended fix involves rejecting pds RPC buffers that are smaller than the required struct fwctl_rpc_pds size prior to accessing any fields within the structure. This approach follows ATT&CK technique T1068 Exploitation for Privilege Escalation and aligns with defensive programming practices that emphasize input validation as a fundamental security control. System administrators should ensure kernel updates are applied promptly to address this vulnerability, while also implementing monitoring solutions to detect anomalous RPC buffer size patterns that might indicate exploitation attempts. The fix essentially implements a boundary check that prevents the system from processing RPC inputs that cannot accommodate the expected data structure, thereby eliminating the potential for out-of-bounds memory access and maintaining kernel stability.