CVE-2026-99170

File disclosure via dropped locked namespace mounts

Published Oct 28, 2026 · Updated Oct 28, 2026

Mount-mask bypass in Linux 7.1 mount namespaces allows local users to read hidden files via crafted mount operations. In fs/namespace.c, MOVE_MOUNT_BENEATH transfers a covering mount's lock to a mount-namespace-file bind that copy_tree() subsequently omits during unshare(CLONE_NEWNS), exposing the underlying file. Exploitation requires root privileges inside a user namespace and a locked file-masking mount; the demonstrated consequence is reading the masked file, not obtaining host root.

CVSS severityUnavailable
Unscored
EPSS probability0.13%
Next 30 days · Nov 1, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Mount-mask bypass in Linux 7.1 mount namespaces allows local users to read hidden files via crafted mount operations. In fs/namespace.c, MOVE_MOUNT_BENEATH transfers a covering mount's lock to a mount-namespace-file bind that copy_tree() subsequently omits during unshare(CLONE_NEWNS), exposing the underlying file. Exploitation requires root privileges inside a user namespace and a locked file-masking mount; the demonstrated consequence is reading the masked file, not obtaining host root.

The record

CVE
CVE-2026-99170
Published
Oct 28, 2026
Updated
Oct 28, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
T1211
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Oct 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Oct 28, 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=7.1
  2. Affected versionversion=c62a4766937edec2962d52e583276b459b739f2d <69fbe94f80bc423613fa18dae6656757423732a2
  3. Affected versionversion=c62a4766937edec2962d52e583276b459b739f2d <bd71d33923b9d6216bcee44331dd37142b0a8441

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=7.1; version=c62a4766937edec2962d52e583276b459b739f2d <69fbe94f80bc423613fa18dae6656757423732a2; version=c62a4766937edec2962d52e583276b459b739f2d <bd71d33923b9d6216bcee44331dd37142b0a8441

Published CVSS scores

No CVSS assessment is available in this record.

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.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1211Exploitation for Defense Evasion

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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