What is CVE-2026-89768?

CVE-2026-89768 is fs: fix user path of nested backing files. The supplied enrichment data classifies it as Unclassified mapped to Not reported.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-89768. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-89768 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

1 public PoC repositories reported; 0 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with Not reported where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-89768 using CVSS null, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

public exploit

CVE-2026-89768

CVE-2026-89768 — fs: fix user path of nested backing files

In the Linux kernel, the following vulnerability has been resolved: fs: fix user path of nested backing files backing_file_open() derives the path to be stored in the new backing file from user_file->f_path. This is incorrect when user_file itself is a backing file, which is the case for nested stacking filesystems, e.g. overlayfs mounts where the lowerdir of one overlayfs is the merged directory of another. Since commit def3ae83da02 ("fs: store real path instead of fake path in backing file f_path") the f_path of a backing file holds the real path of the intermediate layer, not the path that the user opened. Commit 924577e4f6ca ("ovl: Fix nested backing file paths") fixed this for such configurations by passing file_user_path() from ovl_open_realfile(). However, commit 6af36aeb147a ("lsm: add backing_file LSM hooks") changed the first argument of backing_file_open() from the user path back to the user file and derived the path from user_file->f_path again, silently re-introducing the problem. As a result, files mapped through a nested overlayfs show the wrong path in /proc/<pid>/maps and in perf/ftrace mmap records. For example, with two nested overlayfs mounts: mkdir -p /ovl/{lower,upper,work,merged} /ovl/nested echo hello > /ovl/lower/foo mount -t overlay overlay \ -o lowerdir=/ovl/lower,upperdir=/ovl/upper,workdir=/ovl/work \ /ovl/merged # at least two lowerdirs are needed when upperdir is nonexistent mount -t overlay overlay \ -o lowerdir=/ovl/merged:/ovl/lower /ovl/nested mapping /ovl/nested/foo shows a disconnected path instead of the user path: # readlink /proc/self/fd/3 /ovl/nested/foo # grep foo /proc/self/maps 7f6e2c100000-7f6e2c101000 r--s 00000000 00:24 15813027 /foo The bogus path is derived from the f_path of the intermediate backing file, whose mount is a private clone that d_path() cannot resolve. Fix this by using file_user_path(), which returns the outermost user-visible path for backing files and falls back to &user_file->f_path for regular files. This restores the behavior of commit 924577e4f6ca ("ovl: Fix nested backing file paths") for overlayfs and also fixes the same problem for the other backing_file_open() callers, fuse passthrough and erofs ishare, when their user file is itself a backing file. backing_tmpfile_open() has the same pattern but is not affected: it is only called by ovl_create_tmpfile() for the upper layer, and another overlayfs is rejected as upperdir by the DCACHE_OP_REAL check in ovl_mount_dir_check(), so its user_file can never be a backing file.

Published Sep 11, 2026Updated Sep 11, 2026Sources: NVD, Linux (CNA), GitHub, GitHub Security Advisory, Red Hat (VEX), SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Exploit code

public exploit, none observed

EPSS

ahead of 0% of scored CVEs

Affects

Linux

16 products listed

CVSS base

Unscored

no source published a base score

Remediation

The vendor's own words where we have them.

Upgrade Linux to a fixed release (0 to < 7.1). Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

Red Hat VEX · CVE-2026-89768

fixed0affected0not affected1

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
Linux	Linux	5b6aa9a843205da92d860e5011a7b29062a76b8f to < 88c927a63dc717b6d46b20fe13ea713916e49089	Vulnerable
Linux	Linux	5dfcb15974e7d0f96aca278dd9f1b85df91523ef	Vulnerable
Linux	Linux	6af36aeb147a06dea47c49859cd6ca5659aeb987	Vulnerable
Linux	Linux	6af36aeb147a06dea47c49859cd6ca5659aeb987	Vulnerable
Linux	Linux	41c5b269af8b1f0bffcab7766a793f294ae6764e	Vulnerable
Linux	Linux	27e795afba0018b0ea9460dbad4bd706d1ba5ee0	Vulnerable
Linux	Linux	6.12.95 to < 6.12.109	Vulnerable
Linux	Linux	6.18.38 to < 6.18.50	Vulnerable
Linux	Linux	6.6.144 to < 6.7	Vulnerable
Linux	Linux	7.0.4 to < 7.1	Vulnerable
Linux	Linux	7.1	Vulnerable
Linux	Linux	0 to < 7.1	Patched

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
2.3	CVSS 3.1	low	—	—	Red Hat (VEX)

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:N

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Search application, proxy, and WAF logs for requests touching /proc/, /maps, /ftrace, /ovl/, /ovl/nested, /ovl/lower/foo, /ovl/lower,upperdir=/ovl/upper,workdir=/ovl/work, /ovl/merged, /ovl/merged:/ovl/lower, /ovl/nested/foo, /proc/self/fd/3, /proc/self/maps, /foo.
Monitor for scanner or exploit-pattern traffic after 1 public PoC repositories were reported.

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Initial · CVE published
Sep 11, 2026 · NVD
Added · GHSA-xv39-4768-vprw published (unknown)
Sep 11, 2026 · GitHub Security Advisory
CVE published by MITRE.
Sep 11, 2026 · SOCRadar CTI

References

8 on the record

git.kernel.org/stable/c/88c927a63dc717b6d46b20fe13ea713916e49089
Vendor Advisory
git.kernel.org/stable/c/a35cc21355734e1acb89973d9be90ca8e4c3ed2f
Vendor Advisory
git.kernel.org/stable/c/c03114634d342648bd34910aa8fb88007e92cc3c
Vendor Advisory
git.kernel.org/stable/c/f2381b546e7e6a35c9fcee0d0ccb6c042a9aeb5d
Vendor Advisory
nvd.nist.gov/vuln/detail/CVE-2026-89768
NVD
github.com/advisories/GHSA-xv39-4768-vprw
Exploit, Third Party Advisory
access.redhat.com/security/cve/CVE-2026-89768
Vendor Advisory
www.cve.org/CVERecord?id=CVE-2026-89768
Vendor Advisory

Elsewhere on this site

Linuxevery CVE for this vendor
Unclassifiedsame class

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-89768 is fs: fix user path of nested backing files, a unscored vulnerability affecting Linux from Linux. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-89768. Public exploit evidence is: 1 public PoC repositories reported; 0 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS null describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.