Linux Kernel up to 6.17.7/6.18-rc3 NFSD allocation of resources

Summaryinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.17.7/6.18-rc3. Affected by this vulnerability is an unknown functionality of the component NFSD. Performing a manipulation results in allocation of resources. This vulnerability is identified as CVE-2025-40210. There is not any exploit available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as critical, was found in Linux Kernel up to 6.17.7/6.18-rc3. This affects an unknown functionality of the component NFSD. The manipulation with an unknown input leads to a allocation of resources vulnerability. CWE is classifying the issue as CWE-770. The product allocates a reusable resource or group of resources on behalf of an actor without imposing any restrictions on the size or number of resources that can be allocated, in violation of the intended security policy for that actor. The impact remains unknown. The summary by CVE is:

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.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2025-40210 since 04/16/2025. Neither technical details nor an exploit are publicly available.

The vulnerability scanner Nessus provides a plugin with the ID 276562 (Linux Distros Unpatched Vulnerability : CVE-2025-40210), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 6.17.8 or 6.18-rc4 eliminates this vulnerability. Applying the patch b3ee7ce432289deac87b9d14e01f2fe6958f7f0b/3e7f011c255582d7c914133785bbba1990441713 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (276562) and CERT Bund (WID-SEC-2025-2658). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

• Debian Linux
• Amazon Linux 2
• Red Hat Enterprise Linux
• Ubuntu Linux
• SUSE Linux
• Oracle Linux
• SUSE openSUSE
• Open Source Linux Kernel

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.17.0
• 6.17.1
• 6.17.2
• 6.17.3
• 6.17.4
• 6.17.5
• 6.17.6
• 6.17.7
• 6.18-rc1
• 6.18-rc2
• 6.18-rc3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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