CVE-2026-31438: netfs: Fix kernel BUG in netfs_limit_iter() for ITER_KVEC iterators

Severity: medium (CVSS 5.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-22 · updated 2026-06-17
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: netfs: Fix kernel BUG in netfs_limit_iter() for ITER_KVEC iterators When a process crashes and the kernel writes a core dump to a 9P filesystem, __kernel_write() creates an ITER_KVEC iterator. This iterator reaches netfs_limit_iter() via netfs_unbuffered_write(), which only handles ITER_FOLIOQ, ITER_BVEC and ITER_XARRAY iterator types, hitting the BUG() for any other type. Fix this by adding netfs_limit_kvec() following the same pattern as netfs_limit_bvec(), since both kvec and bvec are simple segment arrays with pointer and length fields. Dispatch it from netfs_limit_iter() when the iterator type is ITER_KVEC.

Affected products

Linux kernel: from 6.8 before 6.12.80; from 6.13 before 6.18.21; from 6.19 before 6.19.11; 7.0-rc1, 7.0-rc2, 7.0-rc3, 7.0-rc4, 7.0-rc5, 7.0-rc6 — fixed in 6.12.80, 6.18.21, 6.19.11

How to fix

Upgrade to a fixed version: Linux kernel 6.12.80, 6.18.21, 6.19.11. Check the vendor advisory for mitigations.

References

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