Bug 2536344 (CVE-2026-93096)

Summary: CVE-2026-93096 kernel: cxl/features: Serialize multi-part Get/Set Feature transfers
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in the Linux kernel's CXL features. A concurrency vulnerability exists where multi-part Get/Set Feature transfers are not properly serialized. This allows two concurrent transfers to the same mailbox to interleave their parts, which can corrupt the device's transfer context. A local attacker or privileged process could exploit this to cause system instability or a denial of service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2026-09-17 17:29:53 UTC 
In the Linux kernel, the following vulnerability has been resolved:

cxl/features: Serialize multi-part Get/Set Feature transfers

A Get or Set Feature payload larger than the mailbox payload size is
split into several mailbox commands. mbox_mutex only serializes
individual mailbox commands and is dropped between iterations of these
loops. Nothing serializes the multi-part transfer as a whole.
cxl_get_feature() and cxl_set_feature() are reachable concurrently
from fwctl (per-fd RPCs run under a read-held registration lock) and
from the EDAC scrub/ECS/repair paths, so two transfers to the same
mailbox can interleave their parts and corrupt the device's transfer
context.

Add a per-mailbox feat_mutex and hold it across the whole transfer in
both functions. It nests outside mbox_mutex (which is taken inside
cxl_internal_send_cmd()), and is taken nowhere else, so no lock-ordering
inversion is introduced.
Comment 1 gkamathe 2026-09-19 05:22:48 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-93096.mbox