Integer underflow in Linux kernel - CVE-2026-98446

Vulnerability identifier: #VU156744

CSH Severity: Low

CVSS v4: 6.8 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2026-98446

CWE-ID: CWE-191

Exploitation vector: Local access

Exploit availability: No public exploit available

The vulnerability allows a local user to disrupt filesystem free-space accounting, potentially causing a denial of service.

The vulnerability exists due to an integer underflow in the Linux kernel XFS function xfs_metafile_resv_init when the metadata reservation target falls below the space already used by the metadata btree file. A local user can trigger the affected reservation calculation to cause xfs_dec_fdblocks to subtract an excessively large amount of free space, potentially preventing filesystem space allocations.

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/476582d754cdc5110f806001417fea6c77824c13
• https://git.kernel.org/stable/c/930a9c1c321efdaa3e7f8caecb0479cee3baf342
• https://git.kernel.org/stable/c/f0d8352a39f4a2e329ae45b71bb0d49e2ca0a6dc

• Integer underflow in Linux kernel xfs libxfs
• Ubuntu update for linux-oem-7.0
• Ubuntu update for linux, linux-aws, linux-gcp and more