VulnerabilityPublished 28 Oct 2026

CVE-2026-99155: Linux kernel · scsi: xen/scsifront: Check for a NULL shadow entry on a backend response

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in 15791e57f57f7050014d08cfe239d4aa1e6b94b0 : update Linux kernel when convenient.

Data as of 28 Oct 2026, 10:58 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

Patch: Available – fixed in 15791e57f57f7050014d08cfe239d4aa1e6b94b0, 8c8222c255772713eb36cde695777a1fce224917, 1d91ec793d6c80eca963d426e0da832d40a062df

Exploitation evidence

Disclosed: evidence found.
CVE published 28 Oct 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Linux kernel to 15791e57f57f7050014d08cfe239d4aa1e6b94b0, 8c8222c255772713eb36cde695777a1fce224917 or 1d91ec793d6c80eca963d426e0da832d40a062df.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43, < 15791e57f57f7050014d08cfe239d4aa1e6b94b0	Fixed in 15791e57f57f7050014d08cfe239d4aa1e6b94b0
LinuxLinux	Affected ≥ 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43, < 8c8222c255772713eb36cde695777a1fce224917	Fixed in 8c8222c255772713eb36cde695777a1fce224917
LinuxLinux	Affected ≥ 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43, < 1d91ec793d6c80eca963d426e0da832d40a062df	Fixed in 1d91ec793d6c80eca963d426e0da832d40a062df
LinuxLinux	Affected =5.19	Fixed in–
Debiandebian/linux`pkg:deb/debian/linux`Other threats	Affected =5.19	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

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.

References

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