CVE-2026-31694: fuse: reject oversized dirents in page cache

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-01 · updated 2026-10-23

Description

In the Linux kernel, the following vulnerability has been resolved: fuse: reject oversized dirents in page cache fuse_add_dirent_to_cache() computes a serialized dirent size from the server-controlled namelen field and copies the dirent into a single page-cache page. The existing logic only checks whether the dirent fits in the remaining space of the current page and advances to a fresh page if not. It never checks whether the dirent itself exceeds PAGE_SIZE. As a result, a malicious FUSE server can return a dirent with namelen=4095, producing a serialized record size of 4120 bytes. On 4 KiB page systems this causes memcpy() to overflow the cache page by 24 bytes into the following kernel page. Reject dirents that cannot fit in a single page before copying them into the readdir cache.

Affected products

Linux kernel: from 6.15 before 6.18.25; from 6.19 before 7.0.2; 7.1-rc1, 7.1-rc2 — fixed in 6.18.25, 7.0.2
Siemens Simatic S7-1500 Tm Mfp Firmware: all versions

How to fix

Upgrade to a fixed version: Linux kernel 6.18.25, 7.0.2. Check the vendor advisory for mitigations.

References

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