CVE-2026-97997
Low risk· EPSS 5%Exploitation Probability (EPSS)
Low risk5th percentile - higher than 5% of all known CVEs
Summary
In the Linux kernel, the virtio_ring packed ring handling leaves stale AVAIL and USED descriptor flags after a failed packed add. These descriptors can be misinterpreted by the device as another command entry, blocking the virtqueue. This typically occurs in swiotlb configurations under memory pressure when vring_map_one_sg() fails for larger I/O requests.
Risk Assessment
After a failed add, the device may interpret stale entries as a new command and block the virtio queue, causing I/O stalls or hangs. In swiotlb environments under memory pressure, this can lead to virtual device unavailability and service disruption.
Recommendation
Update the Linux kernel to a version containing the fix for CVE-2026-97997, which invalidates all added descriptors when any add fails in both packed add paths. Until patched, consider reducing memory pressure and monitoring virtio queue errors.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: virtio_ring: fix stale descriptor flags after a failed packed add In a packed ring the AVAIL and USED bits sit in the descriptor itself, so writing them makes that descriptor available. Those bit combinations flip meaning on every round of the ring, tracked by a wrap counter, so invalidating or validating a descriptor means inverting both bits. Commit 1ce9e6055fa0 ("virtio_ring: introduce packed ring support") has virtqueue_add_packed() make every descriptor of a chain available as it maps the chain, and write the head last. The device consumes the ring in order and stops at a head that is not available yet, so it never reaches the rest. When vring_map_one_sg() fails partway, unmap_release unmaps the segments and restores avail_used_flags, but the descriptors it wrote to in the ring stay marked with AVAIL and USED bits. The head is now the only entry that keeps the device from consuming these stale entries. For example, the ring would look like this now. Z - pre-previous command A - previous command B - aborted command C - current command [A1 DONE] [A2 DONE] <C1 EMPTY> [B2] [B3] [Z1 DONE] When the driver now attempts to issue the C command, the next add starts at the same head as B. If C spans less descriptors than B, there is no end marker because AVAIL and USED bits were still in place. And that means the device will start interpreting these stale entries (B2/B3) as another command entry, which then blocks the queue. This effect typically happens in swiotlb configurations under memory pressure, because vring_map_one_sg() can then fail with larger I/O requests which then leads to command abortions. There are broadly 2 ways to avoid leaving those flags behind: 1) Defer those flags too until the chain is complete. 2) Rewrite those flags for the previous wrap counter. Implement the second option in both packed add paths. The first option traverses the chain a second time on every successful add. The second option invalidates all added descriptors when any add fails. With this patch applied, a packed virtqueue keeps completing requests after a failed add.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS