Bug 2461494 (CVE-2026-31614)

Summary: CVE-2026-31614 kernel: smb: client: fix off-by-8 bounds check in check_wsl_eas()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Server Message Block (SMB) client. An untrusted server can exploit an out-of-bounds read vulnerability within the `check_wsl_eas()` function. This flaw allows the server to read up to 8 bytes beyond the intended memory boundary, leading to information disclosure. The leaked kernel memory could potentially disclose sensitive data and influence the interpretation of Windows Subsystem for Linux (WSL) extended attributes.
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Description OSIDB Bzimport 2026-04-24 15:04:50 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix off-by-8 bounds check in check_wsl_eas()

The bounds check uses (u8 *)ea + nlen + 1 + vlen as the end of the EA
name and value, but ea_data sits at offset sizeof(struct
smb2_file_full_ea_info) = 8 from ea, not at offset 0.  The strncmp()
later reads ea->ea_data[0..nlen-1] and the value bytes follow at
ea_data[nlen+1..nlen+vlen], so the actual end is ea->ea_data + nlen + 1
+ vlen.  Isn't pointer math fun?

The earlier check (u8 *)ea > end - sizeof(*ea) only guarantees the
8-byte header is in bounds, but since the last EA is placed within 8
bytes of the end of the response, the name and value bytes are read past
the end of iov.

Fix this mess all up by using ea->ea_data as the base for the bounds
check.

An "untrusted" server can use this to leak up to 8 bytes of kernel heap
into the EA name comparison and influence which WSL xattr the data is
interpreted as.
Comment 1 Keith Grant 2026-04-24 19:56:11 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026042423-CVE-2026-31614-4bf1@gregkh/T