Bug 2540534 (CVE-2026-93785)

Summary:	CVE-2026-93785 kernel: cifs: validate idmap key payload length
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
Version:	unspecified	CC:	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
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the Linux kernel's Common Internet File System (CIFS) implementation. An integer truncation issue in the identity mapping key handler allows a local user to supply an oversized key payload that exceeds the maximum supported length limit. This size discrepancy causes subsequent operations to process the payload with inconsistent boundary lengths, which can lead to memory corruption or a denial of service (DoS).	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
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Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-24 17:09:01 UTC

In the Linux kernel, the following vulnerability has been resolved:

cifs: validate idmap key payload length

The cifs.idmap key type stores its payload length in key->datalen, which
is limited to U16_MAX.  Accepting a larger key payload truncates the
recorded length and can make later users interpret the payload using
inconsistent bounds.

Reject oversized preparsed payloads before allocating or copying them.
This keeps key->datalen consistent with the stored data for both inline
and separately allocated idmap payloads.

Comment 1 Mauro Matteo Cascella 2026-09-28 09:56:36 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-93785.mbox