CVE-2026-64296

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.

Affected Software

References

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