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

xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()

The TX metadata area resides in the UMEM buffer which is memory-mapped
and concurrently writable by userspace. In xsk_skb_metadata(),
csum_start and csum_offset are read from shared memory for bounds
validation, then read again for skb assignment. A malicious userspace
application can race to overwrite these values between the two reads,
bypassing the bounds check and causing out-of-bounds memory access
during checksum computation in the transmit path.

Fix this by reading csum_start and csum_offset into local variables
once, then using the local copies for both validation and assignment.

Note that other metadata fields (flags, launch_time) and the cached
csum fields may be mutually inconsistent due to concurrent userspace
writes, but this is benign: the only security-critical invariant is
that each field's validated value is the same one used, which local
caching guarantees.
Advisories
Source ID Title
Ubuntu USN Ubuntu USN USN-8726-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-8727-1 Linux kernel (OEM) vulnerabilities
Ubuntu USN Ubuntu USN USN-8728-1 Linux kernel (GCP) vulnerabilities
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Mon, 14 Sep 2026 12:00:00 +0000


Thu, 13 Aug 2026 13:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125
CWE-362

Tue, 30 Jun 2026 00:45:00 +0000


Sun, 28 Jun 2026 13:45:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125
CWE-362

Sun, 28 Jun 2026 11:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125
CWE-362

Sun, 28 Jun 2026 08:00:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.8, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'}


Thu, 25 Jun 2026 12:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-125
CWE-362

Thu, 25 Jun 2026 09:15:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata() The TX metadata area resides in the UMEM buffer which is memory-mapped and concurrently writable by userspace. In xsk_skb_metadata(), csum_start and csum_offset are read from shared memory for bounds validation, then read again for skb assignment. A malicious userspace application can race to overwrite these values between the two reads, bypassing the bounds check and causing out-of-bounds memory access during checksum computation in the transmit path. Fix this by reading csum_start and csum_offset into local variables once, then using the local copies for both validation and assignment. Note that other metadata fields (flags, launch_time) and the cached csum fields may be mutually inconsistent due to concurrent userspace writes, but this is benign: the only security-critical invariant is that each field's validated value is the same one used, which local caching guarantees.
Title xsk: cache csum_start/csum_offset to fix TOCTOU in xsk_skb_metadata()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-09-14T11:58:33.282Z

Reserved: 2026-06-09T07:44:35.394Z

Link: CVE-2026-53250

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Modified

Published: 2026-06-25T09:16:42.960

Modified: 2026-09-14T12:17:43.533

Link: CVE-2026-53250

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-06-25T00:00:00Z

Links: CVE-2026-53250 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-08-13T19:15:03Z

Weaknesses