Incorrect authorization in Linux kernel - CVE-2026-98525

Vulnerability identifier: #VU156827

CSH Severity: Low

CVSS v4: 4.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-98525

CWE-ID: CWE-863

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to use and consume another socket's preallocated MCTP tag within the same network namespace.

The vulnerability exists due to improper authorization in mctp_lookup_prealloc_tag() in net/mctp/route.c when processing packets sent with MCTP_TAG_PREALLOC set. A local user can send a packet from a different MCTP socket in the same network namespace with matching network ID, requested tag, and peer address to use and consume a manually allocated tag belonging to another socket because the namespace-wide lookup does not verify socket ownership.

Linux kernel
Ubuntu
linux (Ubuntu package)
linux-aws (Ubuntu package)
linux-gcp (Ubuntu package)
linux-oracle (Ubuntu package)
linux-ibm (Ubuntu package)
linux-hwe-7.0 (Ubuntu package)
linux-oem-7.0 (Ubuntu package)

Install security update from vendor's repository.

Linux kernel - update to 7.0 rc3
linux (Ubuntu package) - update to 7.0.0-42.42
linux-aws (Ubuntu package) - update to 7.0.0-1016.17
linux-gcp (Ubuntu package) - update to 7.0.0-1016.18
linux-oracle (Ubuntu package) - update to 7.0.0-1015.16
linux-ibm (Ubuntu package) - update to 7.0.0-1017.17
linux-hwe-7.0 (Ubuntu package) - update to 7.0.0-42.42~24.04.1
linux-oem-7.0 (Ubuntu package) - update to 7.0.0-1017.17

• https://git.kernel.org/stable/c/09299addab11857e92eca55cd8ef3350b927c90c
• https://git.kernel.org/stable/c/26cc0e69cce062cd3aa6fae33074684669c35a71
• https://git.kernel.org/stable/c/e35cb500dd14882f8dee61783fccd1823fd3ab0d
• https://git.kernel.org/stable/c/f178300e2f56ca9ec2a3a0090608730bbee0af7b

• Incorrect authorization in Linux kernel mctp
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more