CVE-2026-99155 scsi: xen/scsifront: Check for a NULL shadow entry on a backend response
- Exploited in the wild
- Not known
- Fix
- Available
What is CVE-2026-99155?
CVE-2026-99155 is a vulnerability in Linux, published on 28 Oct 2026.
Official description
In the Linux kernel, the following vulnerability has been resolved:
scsi: xen/scsifront: Check for a NULL shadow entry on a backend response
scsifront_do_response() validates the rqid in a backend response against VSCSIIF_MAX_REQS before using it to index info->shadow[], but then dereferences the entry to test ->inflight without checking that the slot is populated. Shadow slots are NULL before a command is submitted (the host private area is zeroed at allocation) and are reset to NULL in _scsifront_put_rqid() once a request completes, so an in-range rqid that does not correspond to an outstanding request makes the frontend dereference a NULL pointer.
A malicious or buggy backend can thus crash the guest by returning a response whose rqid is in range but not in flight -- for example a spurious response before any command has been issued, or a duplicate of one already completed. The ring has only VSCSIIF_MAX_REQS (16) slots, so before the first command every in-range rqid selects a NULL slot.
Reject a response whose shadow slot is not populated.
Which versions are affected by CVE-2026-99155?
How do I fix CVE-2026-99155?
Upgrade to a fixed version.
Is CVE-2026-99155 being exploited?
There is no known exploitation of CVE-2026-99155 in the wild and no public exploit code.
Sources
Also known as AZL-111293, BELL-CVE-2026-99155, DEBIAN-CVE-2026-99155, GHSA-p98p-xmcg-j23c, UBUNTU-CVE-2026-99155.