VulnerabilityPublished 17 Sep 2026Updated 21 Oct 2026

CVE-2026-93186: Linux kernel · cxl/mbox: Clamp mailbox output allocation to the payload size

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in f5d2bbf0300f46307948864fbb97bce5097f4fe2 : update Linux kernel when convenient.

Data as of 26 Oct 2026, 13:47 UTC

Severity

Unrated

Rated by Threat Radar · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 8% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in f5d2bbf0300f46307948864fbb97bce5097f4fe2, d2d40574b9b272ade32d0d77b140d990e7547f5f, b4e11c731d6bee3b87315e055a1ca417c92dc1fc +2

Exploitation evidence

Disclosed: evidence found.
CVE published 17 Sep 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 to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 583fa5e71caeb79e04e477e9837e2f7fa53b71e4, < f5d2bbf0300f46307948864fbb97bce5097f4fe2	Fixed in f5d2bbf0300f46307948864fbb97bce5097f4fe2
LinuxLinux	Affected ≥ 583fa5e71caeb79e04e477e9837e2f7fa53b71e4, < d2d40574b9b272ade32d0d77b140d990e7547f5f	Fixed in d2d40574b9b272ade32d0d77b140d990e7547f5f
LinuxLinux	Affected ≥ 583fa5e71caeb79e04e477e9837e2f7fa53b71e4, < b4e11c731d6bee3b87315e055a1ca417c92dc1fc	Fixed in b4e11c731d6bee3b87315e055a1ca417c92dc1fc
LinuxLinux	Affected ≥ 583fa5e71caeb79e04e477e9837e2f7fa53b71e4, < 31d4841eca7c4b75751ca96d24339e19303337f2	Fixed in 31d4841eca7c4b75751ca96d24339e19303337f2
LinuxLinux	Affected ≥ 583fa5e71caeb79e04e477e9837e2f7fa53b71e4, < 8a13db9f899d149c3aab24abcb668121cfda5a4f	Fixed in 8a13db9f899d149c3aab24abcb668121cfda5a4f
LinuxLinux	Affected =5.12	Fixed in–

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.

References

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