VulnerabilityPublished 11 Sep 2026Updated 5 Oct 2026

CVE-2026-89714: Linux kernel · NFS: fix delegation_hash_table leak when nfs4_server_common_setup() fails

Affects Linux kernelSource GCVE Database

Not known to be exploited.

Data as of 26 Oct 2026, 17:16 UTC

Severity

Medium

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.2% chance of exploitation in 30 days – higher than 10% 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.

ghsa-hv3g-87gw-4m9v

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 properly frees the delegation_hash_table on all error paths in nfs4_server_common_setup(). Users should update to a patched Linux kernel version to resolve this memory leak. Until patched, avoid repeated failed NFSv4 mount attempts against incompatible servers to reduce memory leak impact.

Description

A memory leak vulnerability in the Linux kernel's NFS server implementation occurs when nfs4_server_common_setup() fails during setup. The leak happens because the delegation_hash_table allocated early in the function is not freed on error paths, leading to unreclaimable kernel memory growth. This is triggered by repeated failed NFSv4 mount attempts, such as mounting against an NFSv3-only server. The issue has been resolved in affected Linux kernel versions.

Impact

Repeated failed NFSv4 mount attempts cause a kernel memory leak of approximately 4 KiB per attempt, which can accumulate to multiple gigabytes of unreclaimable slab memory over time. This can degrade system performance and stability due to kernel memory exhaustion. The vulnerability is exploitable trivially from userspace by mounting against incompatible NFS servers.

Summary

The Linux kernel's NFS server code allocates a delegation_hash_table early in the nfs4_server_common_setup() function, but the cleanup callback (server->destroy) responsible for freeing this table is assigned only at the end of the function. If any intermediate step fails (e.g., is_ds_only_client() check, nfs4_init_session(), nfs4_get_rootfh(), or nfs_probe_server()), the function returns with server->destroy still NULL. Consequently, the caller's nfs_free_server() skips freeing the delegation_hash_table, causing a 4 KiB kernel memory leak per failed mount attempt. This leak is trivially reproducible from userspace by repeatedly attempting to mount an NFSv4 share on a server that only supports NFSv3 or has no NFSv4 export path. In production, this caused significant unreclaimable slab memory growth, accumulating multiple gigabytes over time. The fix involves freeing the delegation_hash_table on all error paths between allocation and assignment of server->destroy.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 25 Oct 2026, 03:13 UTC

Technical details

References

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