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CVE.org (no NVD analysis yet)· CNA Linux

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

Noroxi assessment

Priority: Monitor (action score 0/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.18% (FIRST EPSS).
  • Fixed version: Linux Linux 15791e57f57f7050014d08cfe239d4aa1e6b94b0, 1d91ec793d6c80eca963d426e0da832d40a062df, 448b9a8b530b753d346dab10add09a502fc719a4; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 Release Notes.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 15791e57f57f7050014d08cfe239d4aa1e6b94b0, 1d91ec793d6c80eca963d426e0da832d40a062df, 448b9a8b530b753d346dab10add09a502fc719a4; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 Release Notes or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

—No exploit Fix available
Published
Oct 28, 2026
Updated
Oct 30, 2026
EPSS
0.1% · 8th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 5.19affected
    • 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 and later · before 448b9a8b530b753d346dab10add09a502fc719a4affected · git
    • 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 and later · before e397d4da76bed72db6ac4a0848fb6217f8394dcaaffected · git
    • 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 and later · before 90186a2354821329a27d92b266c0f05e8f4f637caffected · git
    • 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 and later · before 1d91ec793d6c80eca963d426e0da832d40a062dfaffected · git
    • 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 and later · before 15791e57f57f7050014d08cfe239d4aa1e6b94b0affected · git
    • 6d1c2f48f3fcf5f42967938c8ba6b42ac6b44b43 and later · before 8c8222c255772713eb36cde695777a1fce224917affected · git
    • before 5.19not affected · semver
    • 6.1.191 and later · up to and including 6.1.*not affected · semver
    • 6.6.161 and later · up to and including 6.6.*not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.115-26.12.115-2

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-99153Oct 28, 2026 · scsi: libiscsi: Validate the ITT reflected in a Reject PDU
    39Monitor
  • ← EarlierCVE-2026-99154Oct 28, 2026 · scsi: libiscsi: Reject a negative task index from parse_pdu_itt
    39Monitor
  • Later →CVE-2026-99156Oct 28, 2026 · scsi: st: Fix use-after-free race between st_remove() and st_open()
    31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux15791e57f57f7050014d08cfe239d4aa1e6b94b0Vendor (CNA)
Linux Linux1d91ec793d6c80eca963d426e0da832d40a062dfVendor (CNA)
Linux Linux448b9a8b530b753d346dab10add09a502fc719a4Vendor (CNA)
Linux Linux8c8222c255772713eb36cde695777a1fce224917Vendor (CNA)
Linux Linux90186a2354821329a27d92b266c0f05e8f4f637cVendor (CNA)
Linux Linuxe397d4da76bed72db6ac4a0848fb6217f8394dcaVendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
azl3 kernel 6.6.159.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
debian:linux6.12.115-2 · Debian:13Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 5, 2026+8 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Technical details

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Exploit maturity— → none
  2. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (5 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records