CVE-2026-63837

Kernel stack disclosure via failed PHC timestamp

Published Jul 19, 2026 · Updated Jul 19, 2026

Information disclosure in the ENA PHC driver in Linux Kernel 6.17 allows local users to read kernel stack data through a PTP ioctl. ena_phc_gettimex64() copies its timestamp output to user space even when ena_com_phc_get_timestamp() fails, exposing uninitialized stack bytes or invalid device values. The path requires local access to a system using the Amazon ENA PHC interface, with failure reachable when PHC is disabled or blocked.

CVSS severity5.5
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Information disclosure in the ENA PHC driver in Linux Kernel 6.17 allows local users to read kernel stack data through a PTP ioctl. ena_phc_gettimex64() copies its timestamp output to user space even when ena_com_phc_get_timestamp() fails, exposing uninitialized stack bytes or invalid device values. The path requires local access to a system using the Amazon ENA PHC interface, with failure reachable when PHC is disabled or blocked.

The record

CVE
CVE-2026-63837
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1005
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=6.17
  2. Affected versionversion=e0ea34158ee8c4f7536cd781010339ff28c0d24c <24a08d7d6218d60c033015cf4870b6096446e734
  3. Affected versionversion=e0ea34158ee8c4f7536cd781010339ff28c0d24c <bddf59818ae5102e6d82a4dae5add6df8da38fb0
  4. Affected versionversion=e0ea34158ee8c4f7536cd781010339ff28c0d24c <edcb049d836e175e7b3d5e0d05657104545b5e65

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linux Kernelversion=6.17; version=e0ea34158ee8c4f7536cd781010339ff28c0d24c <24a08d7d6218d60c033015cf4870b6096446e734; version=e0ea34158ee8c4f7536cd781010339ff28c0d24c <bddf59818ae5102e6d82a4dae5add6df8da38fb0; version=e0ea34158ee8c4f7536cd781010339ff28c0d24c <edcb049d836e175e7b3d5e0d05657104545b5e65

Published CVSS scores

5.5TenableCVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
4.6TenableAV:L/AC:L/Au:S/C:C/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1005Data from Local System

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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