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CVE-2026-98976namespace: keep the lock on a mount that a propagated copy is moved beneath

Description

In the Linux kernel, the following vulnerability has been resolved: namespace: keep the lock on a mount that a propagated copy is moved beneath attach_recursive_mnt() transfers MNT_LOCKED from the top mount to the mount that is moved beneath it with MOVE_MOUNT_BENEATH. This allows the owner of a user namespace to replace its locked /proc or its root. The mount beneath takes on the job of covering the underlying mountpoint allowing the top mount to be unmounted. Consider two mount namespaces: (H) The host H has a shared mount P with a secret in P/d (Z) Z is a user namespace made from M. Its copy of P receives propagation from the host's P and its copy of M's cover on P/d is locked Z's owner must not get to see P/d. Now (H) mounts X on P/d. This propagates into (Z). The copy of X lands beneath (Z)'s locked cover. The locked property is transfered from (Z)'s cover to the copy of X propagated beneath it. The cover is now unlocked. Now (H) unmounts X again. The copy of X in (Z) gets unmounted and the covering mount is left unlocked on top of P/d. (Z) can now unmount it: Z: umount2(P/d) = EINVAL /* the cover is locked */ H: mount X on P/d, umount X /* both propagate into Z /* Z: umount2(P/d) = 0 /* the cover is now unlocked */ Z: read P/d/secret = "covered-by-root" /* secret revealed */ So only transfer the locked property to the mount beneath for mounts the caller has placed. A propagated copy that lands beneath a locked mount is locked as well so that the mount at the bottom of the stack carries a lock the way every check expects. The mount on top of it remains locked to ensure that it keeps covering even if the propagated mount is unmounted again.

Timeline

  1. ID reserved

    By Linux

  2. · 28 days later

    Published

  3. · 1 day later

    Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-98976, by who scored it
Scored byCVSSScoreVector
LinuxCNA (assigner)3.1High7.8CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
NVDNVD · Received3.1High7.8CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
EPSS (exploitation in 30 days)
0.14% · top 97% of all CVEs (14 Nov 2026)
Loading the EPSS history…

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.

Affected products

  • Linux · Linux

    • affected c62a4766937edec2962d52e583276b459b739f2d – < f1f0c24ca701d7d3061c7f69f7450f1734c11745
    • affected c62a4766937edec2962d52e583276b459b739f2d – < d74d66aa708ccf2bc0b1e265a83fed0f2308d5c4

  • Linux · Linux

    • affected 7.1
    • unaffected < 7.1
    • unaffected 7.2.11 – ≤ 7.2.*
    • unaffected 7.3 – ≤ *

References

References2

Sources

The same CVE in the primary databases and aggregators, to check against.

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Record last updated .