Bug 2540558 (CVE-2026-93811)

Summary:	CVE-2026-93811 kernel: ksmbd: Fix acl.sd_buf memory leak and invalid sd_size error handling
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
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 ksmbd Server Message Block (SMB) server. When processing access control list (ACL) data, error-handling routines fail to release memory buffers if decoding fails or if an invalid security descriptor size is encountered. A remote attacker could exploit this vulnerability by repeatedly triggering these error paths, causing memory leaks that may lead to system resource exhaustion and a denial of service (DoS).	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
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 17:14:28 UTC

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

ksmbd: Fix acl.sd_buf memory leak and invalid sd_size error handling

1. When ndr_decode_v4_ntacl() fails, the code jumped to free_n_data
   which only freed n.data, skipping kfree(acl.sd_buf) and leaking
   the buffer. Zero-initialize struct xattr_ntacl acl, reorder error
   labels to out_free to release acl.sd_buf on all error paths.

2. if (acl.sd_size < sizeof(struct smb_ntsd)) is true, original code
   returned success without freeing sd_buf and left stale *pntsd.
   Set rc = -EINVAL before jumping to out_free to return error code and
   free buffer.

Comment 1 Mauro Matteo Cascella 2026-09-28 13:21:22 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-93811.mbox