Bug 2513150 (CVE-2026-68293)

Summary: CVE-2026-68293 kernel: net/mlx5: Fix MCIA register buffer overflow on 32 dword reads
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: medium    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
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Hardware: All   
OS: Linux   
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A flaw was found in the `net/mlx5` driver of the Linux kernel. When the driver attempts to read the MCIA register from a device advertising the `mcia_32dwords` capability, the `mlx5_query_mcia()` function can read more data than the allocated buffer can hold. This leads to a buffer overflow, which can cause a kernel bug and result in a system crash, leading to a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-08-10 12:21:56 UTC 
In the Linux kernel, the following vulnerability has been resolved:

net/mlx5: Fix MCIA register buffer overflow on 32 dword reads

The MCIA register can return up to 32 dwords (128 bytes) when the device
advertises the mcia_32dwords capability, but struct
mlx5_ifc_mcia_reg_bits only defines dword_0..11, leaving room for just
12 dwords (48 bytes) of data.

mlx5_query_mcia() clamps the read size to mlx5_mcia_max_bytes() and then
memcpy()s that many bytes out of the register, potentially reading past
the end of the 'out' buffer. On kernels built with FORTIFY_SOURCE this
is caught as a buffer overflow while reading the module EEPROM via
ethtool:

  detected buffer overflow in memcpy
  kernel BUG at lib/string_helpers.c:1048!
  RIP: 0010:fortify_panic+0x13/0x20
  Call Trace:
   mlx5_query_mcia.isra.0+0x200/0x210 [mlx5_core]
   mlx5_query_module_eeprom_by_page+0x4a/0xa0 [mlx5_core]
   mlx5e_get_module_eeprom_by_page+0xbb/0x120 [mlx5_core]
   eeprom_prepare_data+0xf3/0x170
   ethnl_default_doit+0xf1/0x3b0

Extend the mcia_reg layout to 32 dwords.
Comment 1 gkamathe 2026-08-11 13:00:13 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081028-CVE-2026-68293-a3c8@gregkh/T