cxl/mbox: Clamp mailbox output allocation to the payload size (CVE-2026-93186) | HOL Guard CVE

Unknown severity · Source severity not reportedCVE-2026-93186

cxl/mbox: Clamp mailbox output allocation to the payload size

Answer in brief

CVE-2026-93186 records a Unknown severity vulnerability in cxl/mbox: Clamp mailbox output allocation to the payload size. The current sources do not mark it as known exploited. The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Sep 17, 2026Updated Sep 17, 2026Source checked Sep 17, 2026First seen by HOL Sep 17, 2026Material review Sep 17, 2026

Upstream Advisory

Key facts

Risk: Unknown severitySource severity not reported
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Linux/Linux (generic), Linux/Linux (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Linux/Linuxgeneric	>=583fa5e71caeb79e04e477e9837e2f7fa53b71e4 <f5d2bbf0300f46307948864fbb97bce5097f4fe2 \|\| >=583fa5e71caeb79e04e477e9837e2f7fa53b71e4 <31d4841eca7c4b75751ca96d24339e19303337f2 \|\| >=583fa5e71caeb79e04e477e9837e2f7fa53b71e4 <b4e11c731d6bee3b87315e055a1ca417c92dc1fc \|\| >=583fa5e71caeb79e04e477e9837e2f7fa53b71e4 <8a13db9f899d149c3aab24abcb668121cfda5a4f	f5d2bbf0300f46307948864fbb97bce5097f4fe2, 31d4841eca7c4b75751ca96d24339e19303337f2, b4e11c731d6bee3b87315e055a1ca417c92dc1fc, 8a13db9f899d149c3aab24abcb668121cfda5a4f
Linux/Linuxgeneric	5.12	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Linux/Linux, Linux/Linux.
Review the reported fix. Update Linux/Linux to f5d2bbf0300f46307948864fbb97bce5097f4fe2 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Sep 17, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Sep 17, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Sep 17, 2026

Sources and claim methodology

Upstream source description

In the Linux kernel, the following vulnerability has been resolved: cxl/mbox: Clamp mailbox output allocation to the payload size CXL_MEM_SEND_COMMAND bounds the user's in.size to the mailbox payload size but leaves out.size unbounded, then cxl_mbox_cmd_ctor() calls kvzalloc(out.size). A large out.size drives a huge allocation, above INT_MAX it WARNs and taints, and with panic_on_warn=1 it panics. The transport __cxl_pci_mbox_send_cmd() already clamps the response copy to min(out.size, payload_size, device len), so the output buffer is never written beyond payload_size. Clamp the allocation to payload_size too, matching the RAW path.

Quoted source text, attributed separately from HOL analysis.