Bug 2536241 (CVE-2026-90086)

Summary: CVE-2026-90086 kernel: xsk: honor XDP_TX_METADATA in zero-copy path
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's xsk (AF_XDP) subsystem. The zero-copy path incorrectly reads transmit (TX) metadata even when the XDP_TX_METADATA option is not explicitly set. This can lead to the metadata union being overwritten with an unrequested timestamp, potentially causing data integrity issues or unexpected behavior within the kernel's network processing.
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Description OSIDB Bzimport 2026-09-17 17:05:05 UTC 
In the Linux kernel, the following vulnerability has been resolved:

xsk: honor XDP_TX_METADATA in zero-copy path

The zero-copy path reads TX metadata whenever the UMEM has metadata space,
even if the descriptor does not set XDP_TX_METADATA. Pass descriptor
options through the metadata helpers and ignore metadata unless the option
is set.

This does not fix the existing per-WQE metadata handling for mlx5 MPWQEs.
Only the descriptor that starts a session passes through
xsk_tx_metadata_request() and configures offload state shared by the batch.
Metadata on descriptors joining an open session is therefore not validated
and does not configure its requested offloads. In addition, a non-NULL
metadata pointer from such a descriptor is treated as a timestamp
completion request even when XDP_TXMD_FLAGS_TIMESTAMP is not set, so its
metadata union can be overwritten with an unrequested timestamp. Fixing
mixed metadata states within one MPWQE requires a separate change.
Comment 1 Keith Grant 2026-09-22 19:15:41 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90086.mbox