CVE-2026-63986 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
ethtool: tsinfo: don't pass ERR_PTR to genlmsg_cancel on prepare failure
The goto err label leads to:
genlmsg_cancel(skb, ehdr); return ret;
If ethnl_tsinfo_prepare_dump() failed, it has not started a genlmsg. There's nothing to cancel, and passing an error pointer to genlmsg_cancel() would cause a crash.
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Analysis
by VulDB Data Team • 07/19/2026
This vulnerability exists in the linux kernel's ethtool implementation within the timestamping information handling subsystem. The issue stems from improper error handling during the preparation phase of network timestamping operations. When ethnl_tsinfo_prepare_dump() function fails to prepare the dump operation, the code flow incorrectly attempts to call genlmsg_cancel() with an error pointer returned by the failed function. This represents a classic null pointer dereference scenario where the system tries to process an invalid memory reference, leading to kernel panic and system crash.
The technical flaw manifests in the improper state management of generic netlink message handling structures. During network timestamping information retrieval operations, the kernel creates and manages generic netlink message buffers through genlmsg_cancel() function calls. However, when preparation fails, the error pointer returned by ethnl_tsinfo_prepare_dump() contains no valid message structure for cancellation processing. This violates proper kernel programming practices and creates a direct path to system instability. The vulnerability specifically affects the ethtool subsystem's ability to handle timestamping information queries, which is critical for network monitoring and performance analysis operations.
The operational impact of this vulnerability extends beyond simple system crashes to potentially compromise network infrastructure reliability and availability. Network administrators relying on ethtool for timestamping information collection would experience unexpected kernel panics during normal operations, particularly when querying timestamp capabilities from network interfaces. This could lead to service disruption in production environments where precise timing information is essential for network analysis and troubleshooting activities. The vulnerability affects systems running affected kernel versions where ethtool operations interact with timestamping capabilities, creating a potential denial of service vector that impacts network monitoring tools and applications.
Mitigation strategies should focus on applying the relevant kernel security patches that correct the error handling logic in the ethnl_tsinfo_prepare_dump() function and ensure proper validation before calling genlmsg_cancel(). Organizations should prioritize kernel updates to address this vulnerability while maintaining thorough testing procedures to prevent regression issues. The fix implements proper conditional checks to verify whether a generic netlink message has been properly initialized before attempting cancellation operations, aligning with established secure coding practices for kernel development. This vulnerability demonstrates the importance of proper error handling in kernel-space code and relates to common weakness enumerations such as CWE-476 which addresses null pointer dereference issues. The ATT&CK framework categorizes this under privilege escalation and denial of service techniques where adversaries could exploit similar improper error handling patterns to compromise system stability.