CVE-2025-71128

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

erspan: Initialize options_len before referencing options.

The struct ip_tunnel_info has a flexible array member named

options that is protected by a counted_by(options_len)

attribute.

The compiler will use this information to enforce runtime bounds

checking deployed by FORTIFY_SOURCE string helpers.

As laid out in the GCC documentation, the counter must be

initialized before the first reference to the flexible array

member.

After scanning through the files that use struct ip_tunnel_info

and also refer to options or options_len, it appears the normal

case is to use the ip_tunnel_info_opts_set() helper.

Said helper would initialize options_len properly before copying

data into options, however in the GRE ERSPAN code a partial

update is done, preventing the use of the helper function.

Before this change the handling of ERSPAN traffic in GRE tunnels

would cause a kernel panic when the kernel is compiled with

GCC 15

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References