CVE-2026-64257: smb: client: reject overlapping data areas in SMB2 responses
Greg Kroah-Hartman <[email protected]> Sat, 25 Jul 2026 10:47:54 +0200
| Newsgroups | org.kernel.vger.linux-cve-announce |
|---|---|
| Message-ID | <2026072556-CVE-2026-64257-cdc9@gregkh> |
From: Greg Kroah-Hartman <[email protected]> Description =========== In the Linux kernel, the following vulnerability has been resolved: smb: client: reject overlapping data areas in SMB2 responses Commit 53b7c271f06b ("smb: client: restrict implied bcc[0] exemption to responses without data area") restricted the implied bcc[0] length exception to responses without a data area. However, the overlap handling in __smb2_calc_size() clears data_length, which can make an invalid response appear to have no data area and so qualify for the exception. Track data area overlap separately and reject such responses before applying the length compatibility exceptions. The Linux kernel CVE team has assigned CVE-2026-64257 to this issue. Affected and fixed versions =========================== Issue introduced in 7.2-rc3 with commit 53b7c271f06be4dd5cfc8c6ef552a8355c891a7f and fixed in 7.2-rc4 with commit 8986c932905ea508d66da421eb2eb6e676ace1fe Issue introduced in 5.10.261 with commit 8d0bbc78046d264bbf6a574ea6f9072258a43e35 Issue introduced in 5.15.212 with commit b6a381c01e2ac98a48e32ac0f2a45bbadd9e26b0 Please see https://www.kernel.org for a full list of currently supported kernel versions by the kernel community. Unaffected versions might change over time as fixes are backported to older supported kernel versions. The official CVE entry at https://cve.org/CVERecord/?id=CVE-2026-64257 will be updated if fixes are backported, please check that for the most up to date information about this issue. Affected files ============== The file(s) affected by this issue are: fs/smb/client/smb2misc.c Mitigation ========== The Linux kernel CVE team recommends that you update to the latest stable kernel version for this, and many other bugfixes. Individual changes are never tested alone, but rather are part of a larger kernel release. Cherry-picking individual commits is not recommended or supported by the Linux kernel community at all. If however, updating to the latest release is impossible, the individual changes to resolve this issue can be found at these commits: https://git.kernel.org/stable/c/445ece263131780dee273d727a4d6f11934feec7 https://git.kernel.org/stable/c/36bfa52459e45c0d5b668de2f1c91f6dc5c67775 https://git.kernel.org/stable/c/4a9d2657d3e05f6ed09c148cb127b4e58702275f https://git.kernel.org/stable/c/fdafa1e68dc75045b7b617e6e7d2854950804d83 https://git.kernel.org/stable/c/57cba95f0e97c6f6e45e6731da30aff091bd7460 https://git.kernel.org/stable/c/8986c932905ea508d66da421eb2eb6e676ace1fe