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Vulnerabilities

Vulnerability · CVE-2026-99084

CVE-2026-99084: readdir: take no inode lock on an immutable directory

Published Oct 23, 2026 · catalog updated Oct 23, 2026 · Linux Linux Kernel

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-99084. EPSS is 0.14%. Act only if a listed version of Linux Linux Kernel is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High—
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.14%
Remediation
Not established
Affected products
linux kernel · vendor Linux Linux

In the Linux kernel, the following vulnerability has been resolved: readdir: take no inode lock on an immutable directory iterate_dir() takes the directory's i_rwsem shared and holds it across ->iterate_shared(). For a directory that never has an entry and is never removed the lock keeps nothing still, it only orders every reader and every writer of that inode behind each other. For the directory of a nullfs instance that matters. The instance of the initial mount namespace is the root of every empty mount namespace and the private instance is the root of every kernel thread, so one inode is shared across users who have nothing else in common. And a reader can hold the lock for as long as it likes: back the getdents() buffer with a mapping of a file on a FUSE mount of your own, let the copy of "." and ".." fault and let the server wait. Queue an exclusive taker behind it, a mkdir() in that directory goes through start_dirop() before the read-only mount is reported, and from then on every lookup that misses the dcache in that directory, every create and every mount on it waits until the server answers. One user of an empty mount namespace stalls all the others. Add FOP_IMMUTABLE for the file operations of a directory that never changes and is never removed and let iterate_dir() skip the lock for it. The flag never changes for a file, ->f_pos is protected by f_pos_lock since directories are FMODE_ATOMIC_POS, IS_DEADDIR can't be set on such a directory and neither touch_atime() nor fsnotify take i_rwsem. Set it on the nullfs directory. The placeholder directories of libfs never have an entry either but their owners remove them, so they keep the lock.

Are you affected?

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  • linux kernelversion unspecified
  • vendor Linux Linuxversion unspecified

How to fix CVE-2026-99084

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-99084. EPSS is 0.14%. Act only if a listed version of Linux Linux Kernel is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

No weakness class is stored. EPSS 0.14%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 23, 2026 · Linux Kernel CVE

    Detected

    From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: readdir: take no inode lock on an immutable directory iterate_dir() takes the directory's i_rwsem shared and holds it across ->iterate_shared(). For a directory that never has an entry and is never removed the lock keeps nothing still, it only orders every reader and every writer of

Sources

  • CVE.orgVulnerability recordCVE-2026-99084

    In the Linux kernel, the following vulnerability has been resolved: readdir: take no inode lock on an immutable directory iterate_dir() takes the directory's i_rwsem shared and holds it across ->iterate_shared(). For a directory that never has an entry and is never removed the lo

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-99084

    30-day exploitation probability 0.14%

    first.org
  • Linux Kernel CVEVendor advisoryCVE-2026-99084

    From: Greg Kroah-Hartman Description =========== In the Linux kernel, the following vulnerability has been resolved: readdir: take no inode lock on an immutable directory iterate_dir() takes the directory's i_rwsem shared and holds it across ->iterate_shared(). For a directory th

    git.kernel.org
  • Tenable CVE DatabaseVulnerability recordCVE-2026-99084

    In the Linux kernel, the following vulnerability has been resolved: readdir: take no inode lock on an immutable directory iterate_dir() takes the directory's i_rwsem shared and holds it across ->iterate_shared(). For a directory that never has an entry and is never removed the lock keeps nothing still, it only orders every reader and every writer of that inode behind each other. For the directory

    tenable.com

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSOct 28, 2026
  • Linux Kernel CVEOct 28, 2026
  • Tenable CVE DatabaseOct 23, 2026
  • CVE.orgOct 23, 2026