CVE-2026-63837 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
net: ena: PHC: Check return code before setting timestamp output
ena_phc_gettimex64() is setting the output parameter regardless of whether ena_com_phc_get_timestamp() succeeded or failed.
When ena_com_phc_get_timestamp() returns an error, the timestamp parameter may contain uninitialized stack memory (e.g., when PHC is disabled or in blocked state) or invalid hardware values. Passing these to userspace via the PTP ioctl is both a security issue (information leak) and a correctness bug.
Fix by checking the return code after releasing the lock and only setting the output timestamp on success.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability resides within the Linux kernel's ena network driver implementation, specifically affecting the Precision Time Protocol (PTP) hardware clock functionality. This issue demonstrates a classic improper error handling pattern that can lead to information disclosure and system instability. The ena_phc_gettimex64() function serves as the interface for retrieving precise time stamps from the hardware clock, but fails to properly validate the underlying hardware communication before exposing results to userspace applications.
The technical flaw manifests when the ena_com_phc_get_timestamp() low-level communication function encounters an error condition such as disabled PHC hardware or blocked state operations. In these failure scenarios, the function returns an error code while leaving the timestamp output parameter in an uninitialized state containing stack memory garbage or invalid hardware values. The ena_phc_gettimex64() implementation proceeds to set the output parameter regardless of this error status, creating a scenario where corrupted data gets transmitted through PTP ioctl interfaces to userspace applications.
This vulnerability represents a security risk classified under CWE-248, improper exception handling, and specifically relates to information exposure through uninitialized memory access. The operational impact extends beyond simple correctness issues as malicious actors could potentially exploit this weakness to extract sensitive kernel memory contents or manipulate time synchronization data used by critical system services. When PHC functionality is disabled or enters a blocked state, the uninitialized stack memory may contain remnants of previous operations, creating a potential information leak that violates security boundaries between kernel and user space.
The fix implements proper error code validation following the release of locks, ensuring that timestamp output parameters are only populated when ena_com_phc_get_timestamp() successfully completes its operation. This approach aligns with ATT&CK technique T1083 (File and Directory Discovery) through prevention of unauthorized information access patterns and follows secure coding practices that prevent uninitialized memory exposure. The mitigation strategy directly addresses the root cause by implementing defensive programming principles that validate all system calls and hardware interfaces before propagating results to higher-level applications.
This remediation prevents both the security vulnerability and correctness bug by ensuring proper state management in the driver's PTP implementation. The solution maintains system integrity while preserving legitimate functionality when hardware clocks operate normally, addressing the specific failure modes that could compromise system security through information disclosure channels. The fix demonstrates adherence to kernel security best practices where all external interfaces must validate internal operation success before exposing results to user space, preventing potential exploitation through improper error handling patterns that could otherwise provide attackers with kernel memory contents or system state information.