CVE-2026-89700 - Vulnerability Details

- nfsd: validate sockaddr length per family in listener_set

Description

In the Linux kernel, the following vulnerability has been resolved:

nfsd: validate sockaddr length per family in listener_set

nfsd_sock_nl_policy declares NFSD_A_SOCK_ADDR as a bare NLA_BINARY
attribute with no minimum length. A CAP_NET_ADMIN caller can send a
16-byte NFSD_A_SOCK_ADDR with sa_family=AF_INET6, causing a 12-byte
OOB read across three consumers (rpc_cmp_addr_port, svc_find_listener,
kernel_bind).

nfsd_nl_listener_set_doit() also parsed and validated each listener
entry inline in two separate loops, interleaved with mutating the
running listener configuration. The validation was duplicated, used an
open-coded "nla_len < sizeof(struct sockaddr)" check that was too short
for AF_INET6, and handled a malformed entry inconsistently depending on
which loop noticed it.

Add an nfsd_nl_validate_listeners() helper that walks the entire list
once and confirms each entry parses, carries both an address and a
transport name, and is long enough for its address family
(sizeof(struct sockaddr_in) for AF_INET, sizeof(struct sockaddr_in6)
for AF_INET6, -EAFNOSUPPORT otherwise). Call it before taking
nfsd_mutex or creating the serv, so a malformed request fails cleanly
with no side effects.

Since every entry is known valid by the time the two existing loops
run, drop the redundant presence and per-family length checks from
both, leaving only the nla_parse_nested() call needed to extract the
data.

Published: 2026-09-11

Score: 4.7 Medium

EPSS: < 1% Very Low

KEV: No

Impact:

Action:

Analysis

Impact

The vulnerability is an out‑of‑bounds read in the Linux kernel’s NFS server implementation. A user with CAP_NET_ADMIN can send a malformed NFSD_A_SOCK_ADDR containing a 16‑byte AF_INET6 structure that is too short for the kernel logic, causing three parsing functions to read 12 bytes beyond the buffer. This read exposes arbitrary kernel memory data, which an attacker could use to assist further exploitation. The flaw is a classic CWE‑125 out‑of‑bounds read.

Affected Systems

The affected systems are all Linux kernel installations before the patch that added proper sockaddr length validation in the NFS listener configuration. The advisory does not list specific kernel release numbers, so any host running a pre‑patch kernel is potentially vulnerable. Only the NFS server component contains the vulnerable code path, so only machines that run the NFS server and have CAP_NET_ADMIN privileges are at risk.

Risk and Exploitability

The CVSS score of 4.7 indicates moderate severity. The EPSS score of less than 1% shows the exploitation probability is very low at the time of assessment. The vulnerability requires local privilege (CAP_NET_ADMIN) and is not remotely exploitable, and it is not registered in the CISA KEV catalog. If exploited successfully, the out‑of‑bounds read could reveal kernel memory contents but does not directly lead to code execution; the attacker would still need additional steps to leverage the disclosed information for further compromise.

Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).

Vendor Product Default status Versions

Linux

unaffected

Version	Status	Constraints
`16a471177496c8e04a9793812c187a2c1a2192fa`	affected	< bf85a0f1e45258f90ceeec14772b5769697dfd75
`16a471177496c8e04a9793812c187a2c1a2192fa`	affected	< 2aca70c18c5f5d06004122861fb151d5fcc57faf
`16a471177496c8e04a9793812c187a2c1a2192fa`	affected	< 22d0e4752ca88fd84196d22ebeedc905e6540440
`16a471177496c8e04a9793812c187a2c1a2192fa`	affected	< bdcc85c2b05a9378d8bd2d65f9fc41440a3cf464

Linux

affected

Version	Status	Constraints
`6.10`	affected	—
`0`	unaffected	< 6.10
`6.12.111`	unaffected	≤ 6.12.*
`6.18.50`	unaffected	≤ 6.18.*
`7.2.4`	unaffected	≤ 7.2.*
`7.3-rc1`	unaffected	≤ *

No data.

Vendor Product Confidence Versions

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`[16a471177496c8e04a9793812c187a2c1a2192fa,2aca70c18c5f5d06004122861fb151d5fcc57faf)`	affected	code_commit	—
`[16a471177496c8e04a9793812c187a2c1a2192fa,22d0e4752ca88fd84196d22ebeedc905e6540440)`	affected	code_commit	—
`[16a471177496c8e04a9793812c187a2c1a2192fa,bdcc85c2b05a9378d8bd2d65f9fc41440a3cf464)`	affected	code_commit	—

Linux

Linux Kernel

99%

Version	Status	Scheme	Platform
`6.10`	affected	generic	—
`[0,6.10)`	unaffected	generic	—
`[6.18.50,6.19.0)`	unaffected	semver	—
`[7.2.4,7.3.0)`	unaffected	semver	—
`[7.3-rc1,*]`	unaffected	semver	—

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Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

Upgrade the Linux kernel to a version that includes the nfsd sockaddr length validation fix.
Restrict CAP_NET_ADMIN privileges to trusted administrators to reduce the attack surface.
Disable the NFS server or block listener‑configuration changes if NFS is not required on the host.
Enable auditing of NFS listener configuration changes and review kernel logs for suspicious activity.

Generated by OpenCVE AI on September 15, 2026 at 19:56 UTC.

Tracking

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Advisories

Source	ID	Title
Debian DSA	DSA-6528-1	linux security update

No CVSS v4.0

Attack Vector Local

Attack Complexity High

Privileges Required High

Scope Unchanged

Confidentiality Impact Low

Integrity Impact None

Availability Impact High

User Interaction None

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

The EPSS score is 0.00209.

Key SSVC decision points have not yet been added.

References

Link	Providers
https://git.kernel.org/stable/c/22d0e4752ca88fd84196d22ebeedc905e6540440
https://git.kernel.org/stable/c/2aca70c18c5f5d06004122861fb151d5fcc57faf
https://git.kernel.org/stable/c/bdcc85c2b05a9378d8bd2d65f9fc41440a3cf464
https://git.kernel.org/stable/c/bf85a0f1e45258f90ceeec14772b5769697dfd75
https://nvd.nist.gov/vuln/detail/CVE-2026-89700
https://www.cve.org/CVERecord?id=CVE-2026-89700

History

Mon, 21 Sep 2026 13:30:00 +0000

Type	Values Removed	Values Added
References		https://git.kernel.org/stable/c/bf85a0f1e45258f90ceeec14772b5769697dfd75

Sat, 12 Sep 2026 16:30:00 +0000

Type	Values Removed	Values Added
Weaknesses	CWE-119

Sat, 12 Sep 2026 12:15:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-125
References		https://nvd.nist.gov/vuln/detail/CVE-2026-89700 https://www.cve.org/CVERecord?id=CVE-2026-89700
Metrics	threat_severity `None`	cvssV3_1 `{'score': 4.7, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:N/A:H'}` threat_severity `Important`

Sat, 12 Sep 2026 08:30:00 +0000

Type	Values Removed	Values Added
Weaknesses		CWE-119

Fri, 11 Sep 2026 23:45:00 +0000

Type	Values Removed	Values Added
Description		In the Linux kernel, the following vulnerability has been resolved: nfsd: validate sockaddr length per family in listener_set nfsd_sock_nl_policy declares NFSD_A_SOCK_ADDR as a bare NLA_BINARY attribute with no minimum length. A CAP_NET_ADMIN caller can send a 16-byte NFSD_A_SOCK_ADDR with sa_family=AF_INET6, causing a 12-byte OOB read across three consumers (rpc_cmp_addr_port, svc_find_listener, kernel_bind). nfsd_nl_listener_set_doit() also parsed and validated each listener entry inline in two separate loops, interleaved with mutating the running listener configuration. The validation was duplicated, used an open-coded "nla_len < sizeof(struct sockaddr)" check that was too short for AF_INET6, and handled a malformed entry inconsistently depending on which loop noticed it. Add an nfsd_nl_validate_listeners() helper that walks the entire list once and confirms each entry parses, carries both an address and a transport name, and is long enough for its address family (sizeof(struct sockaddr_in) for AF_INET, sizeof(struct sockaddr_in6) for AF_INET6, -EAFNOSUPPORT otherwise). Call it before taking nfsd_mutex or creating the serv, so a malformed request fails cleanly with no side effects. Since every entry is known valid by the time the two existing loops run, drop the redundant presence and per-family length checks from both, leaving only the nla_parse_nested() call needed to extract the data.
Title		nfsd: validate sockaddr length per family in listener_set
First Time appeared		Linux Linux linux Kernel
CPEs		cpe:2.3:o:linux:linux_kernel::::::::
Vendors & Products		Linux Linux linux Kernel
References		https://git.kernel.org/stable/c/22d0e4752ca88fd84196d22ebeedc905e6540440 https://git.kernel.org/stable/c/2aca70c18c5f5d06004122861fb151d5fcc57faf https://git.kernel.org/stable/c/bdcc85c2b05a9378d8bd2d65f9fc41440a3cf464

Subscriptions

Linux Linux Kernel

MITRE

Status: PUBLISHED

Assigner: Linux

Published: 2026-09-11T19:46:18.076Z

Updated: 2026-09-21T13:14:50.652Z

Reserved: 2026-09-11T19:38:34.750Z

Link: CVE-2026-89700

Vulnrichment

No data.

NVD

Status : Received

Published: 2026-09-11T20:19:57.187

Modified: 2026-09-21T14:17:25.580

Link: CVE-2026-89700

Redhat

Severity : Important

Publid Date: 2026-09-11T19:46:18Z

Links: CVE-2026-89700 - Bugzilla

OpenCVE Enrichment

Updated: 2026-09-15T20:00:08Z

Weaknesses

CWE-125
Out-of-bounds Read

Impact

Affected Systems

Risk and Exploitability

Tracking

Attack Vector Local

Attack Complexity High

Privileges Required High

Scope Unchanged

Confidentiality Impact Low

Integrity Impact None

Availability Impact High

User Interaction None

Subscriptions

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