CVE-2026-63837
Received Received - Intake

Linux Kernel PHC Timestamp Output Validation Flaw

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

Description
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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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-63837
EUVD
EUVD-2026-45521

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a function called ena_phc_gettimex64() which incorrectly sets a timestamp output parameter even when an error occurs. The function ena_com_phc_get_timestamp() may fail and return an error, but the timestamp value could still be set to uninitialized stack memory or invalid hardware data. This leads to both a security issue where sensitive data might leak and a correctness problem in the timestamp output.

Detection Guidance

This vulnerability affects the Linux kernel's ENA (Elastic Network Adapter) PHC (Precision Time Protocol Hardware Clock) functionality. Detection requires checking kernel logs for errors related to ena_phc_gettimex64 or PHC operations. Use commands like 'dmesg | grep ena' or 'journalctl -k | grep ena' to inspect kernel logs for ENA-related errors.

Impact Analysis

If you use a system running the affected Linux kernel version, this vulnerability could allow unauthorized access to sensitive memory contents through the timestamp output. It may also cause incorrect timestamps to be reported, affecting time-sensitive operations. Systems using the ENA (Elastic Network Adapter) driver are particularly at risk.

Compliance Impact

This vulnerability could lead to information leaks, which may violate data protection regulations like GDPR or HIPAA if sensitive data is exposed. Incorrect timestamps might also affect audit logs or time-stamped records, potentially leading to compliance issues if accurate logging is required.

Mitigation Strategies

Update the Linux kernel to a patched version that includes the fix for CVE-2026-63837. If immediate patching is not possible, disable the ENA PHC feature by setting the kernel parameter 'ena_phc_disable=1' or unloading the ena module if not in use.

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