CVE-2026-64553 in Linux
Summary
by MITRE • 07/27/2026
In the Linux kernel, the following vulnerability has been resolved:
net: psample: fix info leak in PSAMPLE_ATTR_DATA
psample open codes nla_put() presumably to avoid wiping the data with 0s just to override it with packet data. This open coding is missing clearing the pad, however, each netlink attr is padded to 4B and data_len may not be divisible by 4B.
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Analysis
by VulDB Data Team • 07/27/2026
The vulnerability identified in the Linux kernel's psample subsystem represents a critical information disclosure issue that stems from improper memory handling during netlink attribute construction. This flaw exists within the PSAMPLE_ATTR_DATA attribute processing mechanism where the kernel employs open coding of nla_put() functions to optimize performance by avoiding unnecessary zeroing operations. The technical implementation fails to properly clear padding bytes when constructing netlink attributes, creating a scenario where residual data from previous operations may persist in memory regions intended for packet data transmission.
The core technical flaw manifests when the psample subsystem processes packet samples through netlink communication channels. Each netlink attribute is required to be padded to 4-byte boundaries for alignment purposes according to standard network protocol specifications. When the actual data length does not align perfectly with these 4-byte boundaries, the padding bytes that follow the legitimate data payload remain uninitialized or contain residual information from previous memory allocations. This open coding approach bypasses the normal attribute clearing mechanisms that would otherwise ensure all padding bytes are properly zeroed before data insertion.
The operational impact of this vulnerability extends beyond simple information leakage to potentially expose sensitive kernel memory contents including cryptographic keys, session identifiers, or other confidential data structures that may have resided in the affected memory regions. Attackers could exploit this weakness by crafting specific packet samples that trigger the vulnerable code path, allowing them to extract unintended information from kernel memory spaces through carefully constructed netlink attribute processing. This type of information disclosure vulnerability directly violates the principle of least privilege and can provide attackers with valuable insights for further exploitation attempts.
From a cybersecurity perspective, this vulnerability maps to CWE-248, which addresses "Uncaught Exception" in software systems where improper handling of data structures leads to unintended information exposure. The ATT&CK framework categorizes this as a technique involving information gathering through kernel memory analysis, potentially enabling more sophisticated attacks such as privilege escalation or advanced persistent threat operations. The vulnerability demonstrates how performance optimization decisions can introduce security flaws when proper memory management practices are bypassed. Mitigation strategies should focus on implementing proper padding clearing mechanisms during attribute construction, ensuring that all netlink attribute processing adheres to standard memory initialization protocols while maintaining performance requirements through more secure coding patterns.
The fix for this vulnerability requires modifications to the psample subsystem's attribute handling code to ensure that padding bytes are properly cleared before data insertion occurs. This involves either restoring normal nla_put() behavior with appropriate zeroing or implementing explicit padding clearing logic that operates correctly regardless of data length alignment. The solution must balance performance considerations with security requirements, ensuring that the memory management practices maintain kernel stability while eliminating the information disclosure risk. Organizations should prioritize patching this vulnerability as it represents a fundamental security weakness in kernel network processing that could be exploited by sophisticated attackers to gain unauthorized access to sensitive system information.