VulnerabilityPublished 11 Sep 2026Updated 5 Oct 2026

CVE-2026-89768: Linux kernel · fs: fix user path of nested backing files

Affects Linux kernelSource GCVE Database

Not known to be exploited.

Data as of 26 Oct 2026, 13:47 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation evidence

Disclosed: evidence found.
CVE published 11 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Ubuntu 26.04 LTSlinux`pkg:deb/ubuntu/linux?arch=source&distro=resolute`Other threats	Affected 6.17.0-5.5 – 7.0.0-38.38 23 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-aws`pkg:deb/ubuntu/linux-aws?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure`pkg:deb/ubuntu/linux-azure?arch=source&distro=resolute`Other threats	Affected 6.17.0-1003.3 – 7.0.0-1017.17 15 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-azure-fde`pkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resolute`Other threats	Affected 7.0.0-1003.3 – 7.0.0-1016.16 9 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gcp`pkg:deb/ubuntu/linux-gcp?arch=source&distro=resolute`Other threats	Affected 6.17.0-1002.2 – 7.0.0-1014.14 13 affected builds	Fixed in–
Ubuntu 26.04 LTSlinux-gke`pkg:deb/ubuntu/linux-gke?arch=source&distro=resolute`Other threats	Affected 7.0.0-1002.3 – 7.0.0-1008.9 6 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available that restores the use of file_user_path() in backing_file_open() to correctly derive the user-visible path for nested backing files. Users should apply the updated Linux kernel versions that include this fix. Since this is a kernel-level fix, upgrading to patched kernel versions is the recommended remediation.

Description

A vulnerability in the Linux kernel's handling of nested backing files in overlayfs and similar stacking filesystems causes incorrect user path reporting. The issue arises because backing_file_open() derives the file path from an intermediate backing file's f_path, which holds the real path of the intermediate layer rather than the user-visible path. This results in incorrect paths shown in /proc/<pid>/maps and in perf/ftrace mmap records for files accessed through nested overlayfs mounts. The problem was reintroduced by a recent commit that changed how backing_file_open() derives the path. The fix restores the use of file_user_path() to obtain the correct user-visible path, resolving the issue for overlayfs and other backing_file_open() callers like fuse passthrough and erofs ishare.

Impact

The vulnerability causes incorrect file path information to be shown in process memory maps (/proc/<pid>/maps) and in performance tracing tools (perf/ftrace mmap records) when files are accessed through nested overlayfs mounts or similar stacking filesystems. This can lead to confusion or misinterpretation of file mappings by users or tools relying on accurate path information. There is no indication of direct security compromise or code execution from this issue.

Summary

The Linux kernel vulnerability CVE-2026-89768 involves incorrect path derivation for nested backing files in stacking filesystems such as overlayfs. backing_file_open() incorrectly uses user_file->f_path to derive the path, which is invalid when user_file is itself a backing file, causing user-visible paths to be replaced by intermediate backing file paths that cannot be resolved properly. This leads to misleading path information in process memory maps and tracing tools. The issue was introduced by a commit that changed backing_file_open() to derive the path from user_file->f_path again, undoing a previous fix. The vulnerability affects nested overlayfs mounts and similar configurations. The fix uses file_user_path() to retrieve the outermost user-visible path, restoring correct path reporting for nested backing files.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Oct 2026, 03:42 UTC

Technical details

References

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