CVE-2026-68120 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
rtase: Workaround for TX hang caused by hardware packet parsing
The hardware performs packet parsing before packet transmission. Parsing incomplete IPv4, IPv6, TCP, or UDP headers may trigger a TX hang because the hardware parser expects additional protocol header data that is not present in the packet.
The hardware performs additional PTP parsing on UDP packets identified by destination ports 319/320 at the expected UDP destination port offset.
If such a packet has transport data smaller than RTASE_MIN_PAD_LEN, the hardware parser expects additional packet data and may trigger a TX hang.
To avoid these hardware issues, the driver applies the following workarounds.
Drop malformed packets that may trigger this hardware issue before transmission.
For IPv4 non-initial fragments, the hardware does not check the fragment offset before parsing the expected transport header location. As a result, these packets are still subject to transport header parsing even though they do not contain a transport header. If the transport data is shorter than the minimum transport header required by the hardware parser, pad the transport data to the minimum transport header length required by the hardware parser. Packets that also match the hardware PTP parsing conditions continue to follow the corresponding workaround.
For IPv6 fragmented packets, neither of the above hardware issues occurs because the hardware only continues packet parsing when the IPv6 Base Header Next Header field directly indicates UDP. Packets carrying a Fragment Header do not continue through the subsequent packet parsing stages.
For packets identified for hardware PTP parsing, pad the transport data so it reaches RTASE_MIN_PAD_LEN before transmission.
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Analysis
by VulDB Data Team • 08/10/2026
The vulnerability in question affects the Linux kernel's rtase driver which handles network packet transmission through hardware acceleration. This issue represents a critical hardware-level flaw that can cause complete transmission hangs during packet processing. The problem stems from the interaction between software packet handling and hardware packet parsing mechanisms within the network interface controller. When packets are processed by the hardware parser, incomplete protocol headers trigger unexpected behavior that results in system-wide transmission failures.
The technical root cause involves the hardware's pre-transmission packet parsing process which operates before packets are actually sent over the network. For IPv4 and IPv6 protocols, the hardware parser expects complete header structures to be present at specific offsets within the packet data stream. When parsing incomplete headers for IPv4 non-initial fragments or UDP packets with transport data below minimum thresholds, the hardware becomes stuck in an infinite loop attempting to locate expected protocol data that simply does not exist. This behavior manifests as transmission hangs because the hardware parser blocks further processing until it receives the complete header structure it anticipates.
The vulnerability specifically targets certain network protocols and port combinations where the hardware performs additional PTP (Precision Time Protocol) parsing on UDP packets destined for ports 319 and 320. These port numbers are commonly used in time synchronization applications, making this issue particularly relevant for network infrastructure systems that rely on precise timing mechanisms. When such packets contain transport data smaller than RTASE_MIN_PAD_LEN, the hardware parser enters a problematic state where it expects additional packet data to complete its parsing sequence, ultimately causing the transmission channel to hang.
The mitigation strategy implemented by the kernel developers addresses this issue through multiple layered approaches that handle different packet types and conditions. The primary workaround involves dropping malformed packets before they reach the problematic hardware parsing stage, preventing the system from encountering these edge cases entirely. For IPv4 non-initial fragments, the solution pads transport data to meet minimum header requirements while maintaining compatibility with existing network protocols. This padding approach ensures that the hardware parser encounters sufficient data to complete its processing without triggering the hang condition.
The implementation also addresses IPv6 fragmented packets through a different mechanism since the hardware behavior differs between IPv4 and IPv6 protocols. In IPv6 cases, the hardware only continues parsing when the Next Header field directly indicates UDP protocol, meaning packets with Fragment Headers do not proceed to subsequent parsing stages where the issue would occur. This distinction demonstrates how different protocol implementations can present varying levels of vulnerability to the same underlying hardware flaw.
The solution aligns with common security practices for handling malformed input data in network processing systems and follows established patterns for mitigating hardware-level vulnerabilities through software workarounds. This approach prevents denial-of-service conditions while maintaining network functionality, though it does introduce additional overhead through packet validation and padding operations. The fix demonstrates the importance of understanding hardware behavior when implementing network drivers and highlights how protocol-specific parsing requirements can create unexpected system vulnerabilities.
From a cybersecurity perspective, this vulnerability represents a classic example of how hardware-level design decisions can create exploitable conditions in network infrastructure. The issue affects systems that rely on accelerated network processing and could potentially be exploited to cause service disruption through carefully crafted malformed packets. The fix maintains backward compatibility while preventing the specific parsing conditions that lead to system hangs, demonstrating effective risk mitigation for hardware-level vulnerabilities.
This vulnerability analysis demonstrates how low-level driver implementations must account for hardware-specific behaviors and edge cases in protocol handling. The approach taken by the Linux kernel developers reflects standard security practices for addressing hardware-level issues through software mitigations, ensuring system stability while maintaining network performance. The solution also highlights the complexity of modern network processing systems where software and hardware components interact in ways that can create unexpected vulnerabilities.
The technical implementation follows industry standards for handling malformed packet data and provides a robust solution for preventing transmission hangs while maintaining network functionality. This approach prevents potential exploitation through malformed packets and ensures that network systems remain operational under various protocol conditions. The fix represents a mature response to hardware-level issues that demonstrates the importance of comprehensive testing and validation in network driver development.
The vulnerability's impact extends beyond simple transmission failures, affecting overall system reliability and network availability for applications that depend on continuous packet flow. By implementing these workarounds, the Linux kernel ensures that systems remain stable even when encountering edge cases in hardware packet processing, maintaining operational integrity while preventing potential denial-of-service conditions that could affect critical network infrastructure components.