AI description
CVE-2026-31694 is identified as a buffer overflow vulnerability within the Linux Kernel's Filesystem in Userspace (FUSE) subsystem. The flaw specifically resides in the `fuse_add_dirent_to_cache()` function. This function is responsible for constructing and copying serialized directory entries into a page-cache page. The vulnerability occurs because `fuse_add_dirent_to_cache()` does not adequately validate that a serialized directory entry will fit entirely within a single page-cache page before performing the copy operation. A malicious FUSE server can exploit this by providing an oversized directory entry, such as one with `namelen=4095`, which results in a 4120-byte record. On systems utilizing 4 KiB pages, this oversized record can cause a 24-byte overflow into the adjacent kernel page. This issue impacts various Linux kernel versions, including 7.1-rc1 and 7.1-rc2.
- 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.
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
- NVD status
- Analyzed
- Products
- linux_kernel
CVSS 3.1
- Type
- Secondary
- Base score
- 7.8
- Impact score
- 5.9
- Exploitability score
- 1.8
- Vector string
- CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Severity
- HIGH
Hype score is a measure of social media activity compared against trending CVEs from the past 12 months. Max score 100.
- Hype score
10
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