🛡️ CVE-2025-40210 — kernel

🟠 CVSS 7.5 — High ✅ No Known Exploit NVD
7.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Revert "NFSD: Remove the cap on number of operations per NFSv4 COMPOUND"

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

Revert "NFSD: Remove the cap on number of operations per NFSv4 COMPOUND"

I've found that pynfs COMP6 now leaves the connection or lease in a

strange state, which causes CLOSE9 to hang indefinitely. I've dug

into it a little, but I haven't been able to root-cause it yet.

However, I bisected to commit 48aab1606fa8 ("NFSD: Remove the cap on

number of operations per NFSv4 COMPOUND").

Tianshuo Han also reports a potential vulnerability when decoding

an NFSv4 COMPOUND. An attacker can place an arbitrarily large op

count in the COMPOUND header, which results in:

[ 51.410584] nfsd: vmalloc error: size 1209533382144, exceeds total

pages, mode:0xdc0(GFP_KERNEL|__GFP_ZERO),

nodemask=(null),cpuset=/,mems_allowed=0

when NFSD attempts to allocate the COMPOUND op array.

Let's restore the operation-per-COMPOUND limit, but increased to 200

for now.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Affected software

CVE-2025-40210 is recorded against 2 packages.

  • kernel (from 6.17.0 up to 6.17.8)
  • unknown

Timeline and source

Published on 21 November 2025 and last revised on 6 August 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

git.kernel.org (Web)
git.kernel.org (Web)
github.com (Advisory)
nvd.nist.gov (Advisory)
git.kernel.org (Package)

CVE-2025-40210 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity High
CVSS Score 7.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE N/A
Public Exploit ✅ No
Source NVD
Published 2025-11-21
Updated 2026-08-12
Modified 2026-08-06
Fix URL N/A

Affected Packages

Software From version Fixed in
kernel 6.17.0 6.17.8
unknown — —

Similar Threats

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