CVE-2024-49996: cifs: Fix buffer overflow when parsing NFS reparse points

Vulnerability summary

CVE-2024-49996 is a critical (CVSS 9.4) vulnerability in debian debian_linux. EPSS estimates a 0.78% chance of exploitation in the next 30 days, higher than 56% of scored vulnerabilities.

Timeline

1. 21-10-2024
   PublishedVulnerability first disclosed.
2. 05-08-2026
   Last modifiedVulnerability information updated.

Description

In the Linux kernel, the following vulnerability has been resolved: cifs: Fix buffer overflow when parsing NFS reparse points ReparseDataLength is sum of the InodeType size and DataBuffer size. So to get DataBuffer size it is needed to subtract InodeType's size from ReparseDataLength. Function cifs_strndup_from_utf16() is currentlly accessing buf->DataBuffer at position after the end of the buffer because it does not subtract InodeType size from the length. Fix this problem and correctly subtract variable len. Member InodeType is present only when reparse buffer is large enough. Check for ReparseDataLength before accessing InodeType to prevent another invalid memory access. Major and minor rdev values are present also only when reparse buffer is large enough. Check for reparse buffer size before calling reparse_mkdev().

• CWE-120Buffer Copy without Checking Size of InputThe 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.