CVE-2025-38566Network attack vector

NFS server crash via out-of-bounds kvec access

Published Aug 19, 2025 · Updated Aug 5, 2026

Out-of-bounds access in the Linux kernel allows remote attackers to crash NFS servers by sending a crafted TLS alert. In tls_alert_recv(), a two-byte RPC fragment marker can exhaust the stack-backed kvec, but the advanced iterator is reused for the alert payload, so stale stack data is treated as another buffer pointer. The NFS-over-TLS service must be listening on TCP port 2049; the path is reachable before client authentication and can expose a teardown oracle or fault an nfsd thread.

CVSS severity9.8
Critical
EPSS probability0.59%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds access in the Linux kernel allows remote attackers to crash NFS servers by sending a crafted TLS alert. In tls_alert_recv(), a two-byte RPC fragment marker can exhaust the stack-backed kvec, but the advanced iterator is reused for the alert payload, so stale stack data is treated as another buffer pointer. The NFS-over-TLS service must be listening on TCP port 2049; the path is reachable before client authentication and can expose a teardown oracle or fault an nfsd thread.

The record

CVE
CVE-2025-38566
Published
Aug 19, 2025
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-754, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 19, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5e052dda121e2870dd87181783da4a95d7d2927b <25bb3647d30a20486b5fe7cff2b0e503c16c9692
  2. Affected versionversion=5e052dda121e2870dd87181783da4a95d7d2927b <3b549da875414989f480b66835d514be80a0bd9c
  3. Affected versionversion=5e052dda121e2870dd87181783da4a95d7d2927b <6b33c31cc788073bfbed9297e1f4486ed73d87da
  4. Affected versionversion=5e052dda121e2870dd87181783da4a95d7d2927b <b1df394621710b312f0393e3f240fdac0764f968
  5. Affected versionversion=5e052dda121e2870dd87181783da4a95d7d2927b <bee47cb026e762841f3faece47b51f985e215edb
  6. Affected versionversion=6.4

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5e052dda121e2870dd87181783da4a95d7d2927b <25bb3647d30a20486b5fe7cff2b0e503c16c9692; version=5e052dda121e2870dd87181783da4a95d7d2927b <3b549da875414989f480b66835d514be80a0bd9c; version=5e052dda121e2870dd87181783da4a95d7d2927b <6b33c31cc788073bfbed9297e1f4486ed73d87da; version=5e052dda121e2870dd87181783da4a95d7d2927b <b1df394621710b312f0393e3f240fdac0764f968; version=5e052dda121e2870dd87181783da4a95d7d2927b <bee47cb026e762841f3faece47b51f985e215edb; version=6.4

Published CVSS scores

9.8Linux kernel CVE teamCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-754Improper Check for Unusual or Exceptional Conditions
T1499.004Application or System Exploitation Flood

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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