CVE-2026-98525

/// Technical description

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

mctp: route: iterate socket tag list in mctp_lookup_prealloc_tag()

When a socket transmits a packet with MCTP_TAG_PREALLOC set,

mctp_lookup_prealloc_tag() iterates over the per-netns &mns->keys list

and matches netid, req_tag, peer_addr, and manual_alloc, without

checking whether tmp->sk == &msk->sk. This allows any MCTP socket in the

same network namespace to use and consume another socket's preallocated

tag.

Iterate the socket's own tag list (&msk->keys via sklist) instead of the

namespace-wide &mns->keys list in mctp_lookup_prealloc_tag(), ensuring

that only tags allocated by msk are matched.

Tested in QEMU against Linux 7.3.0-rc3 by allocating a manual tag

(0x18) on socket A via SIOCMCTPALLOCTAG for peer EID 9 and sending a

4-byte message with MCTP_TAG_PREALLOC from socket B in the same network

namespace. On the unfixed kernel, sendto(sock_b) using socket A's

preallocated tag succeeds (ret = 4); with this patch

/// 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