Linux Kernel up to 7.2.7/7.3-rc3 SMB Client memcpy buffer overflow

Summaryinfo

A vulnerability classified as very critical was found in Linux Kernel up to 7.2.7/7.3-rc3. This issue affects the function memcpy of the component SMB Client. Such manipulation leads to buffer overflow. This vulnerability is documented as CVE-2026-98318. The attack can be executed remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Linux Kernel up to 7.2.7/7.3-rc3 and classified as very critical. Affected by this issue is the function memcpy of the component SMB Client. The manipulation with an unknown input leads to a buffer overflow vulnerability. Using CWE to declare the problem leads to CWE-120. The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: smb: client: validate absolute native symlink targets before NT fixups With symlinkroot unset, an absolute target is copied without conversion to an NT drive path. Later code still assumes an NT prefix is present when modifying the target and calculating the print name length. For "/ab", this causes two failures: sym[5] and path[5] are written past their allocations, and plen -= 2 * poff subtracts an assumed 8-byte prefix from a 6-byte UTF-16 target, wrapping u16 plen to 65534. That underflow causes another overflow: memcpy() copies 65534 bytes into a 24-byte buffer. A user with write access to a mounted share can trigger these bugs with default settings. Validate the NT drive prefix, including an ASCII drive letter, before accessing fixed offsets or subtracting the prefix length.

The advisory is shared for download at git.kernel.org. This vulnerability is handled as CVE-2026-98318 since 09/25/2026. The exploitation is known to be easy. The attack may be launched remotely. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $5k-$25k (estimation calculated on 10/06/2026).

Upgrading to version 7.2.8 or 7.3-rc4 eliminates this vulnerability. Applying the patch 6913ff607c2bc8694193e1fcc40bf16d75f35f16/23c240d9509e15f72e4112fc95f0160ab32ec430 is able to eliminate this problem. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 7.2.0
• 7.2.1
• 7.2.2
• 7.2.3
• 7.2.4
• 7.2.5
• 7.2.6
• 7.2.7
• 7.3-rc1
• 7.3-rc2
• 7.3-rc3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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