Linux Kernel up to 6.18.13/6.19.3 NFS stack-based overflow

Summaryinfo

A vulnerability labeled as critical has been found in Linux Kernel up to 6.18.13/6.19.3. Affected by this issue is some unknown functionality of the component NFS. Executing a manipulation can lead to stack-based overflow. This vulnerability is tracked as CVE-2026-46256. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 6.18.13/6.19.3. This vulnerability affects an unknown part of the component NFS. The manipulation with an unknown input leads to a stack-based overflow vulnerability. The CWE definition for the vulnerability is CWE-121. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function). As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: NFS/localio: prevent direct reclaim recursion into NFS via nfs_writepages LOCALIO is an NFS loopback mount optimization that avoids using the network for READ, WRITE and COMMIT if the NFS client and server are determined to be on the same system. But because LOCALIO is still fundamentally "just NFS loopback mount" it is susceptible to recursion deadlock via direct reclaim, e.g.: NFS LOCALIO down to XFS and then back into NFS via nfs_writepages. Fix LOCALIO's potential for direct reclaim deadlock by ensuring that all its page cache allocations are done from GFP_NOFS context. Thanks to Ben Coddington for pointing out commit ad22c7a043c2 ("xfs: prevent stack overflows from page cache allocation").

The advisory is available at git.kernel.org. This vulnerability was named CVE-2026-46256 since 05/13/2026. The exploitation appears to be easy. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 06/03/2026).

Upgrading to version 6.18.14 or 6.19.4 eliminates this vulnerability. Applying the patch ae26a4cf2baf0a44c538dc093504d1994b02dade/6a5de0c4fc0f217eea945d3d72c34ee30d72cbc9/67435d2d8a33a75f9647724952cb1b18279d2e95 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.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 6.18.0
• 6.18.1
• 6.18.2
• 6.18.3
• 6.18.4
• 6.18.5
• 6.18.6
• 6.18.7
• 6.18.8
• 6.18.9
• 6.18.10
• 6.18.11
• 6.18.12
• 6.18.13
• 6.19.0
• 6.19.1
• 6.19.2
• 6.19.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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