Bug 2507145 (CVE-2026-64380)

Summary:	CVE-2026-64380 kernel: smb: client: harden POSIX SID length parsing
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, 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 Server Message Block (SMB) client. The vulnerability exists in the `posix_info_sid_size()` function, which is responsible for parsing POSIX Security Identifiers (SIDs). An insufficient boundary check allows the system to accept truncated POSIX SIDs, which could lead to unexpected behavior or a denial of service. This issue has been resolved by requiring at least two bytes before reading the subauthority count, ensuring that all client paths safely reject malformed SIDs.	Story Points:	---
Clone Of:		Environment:
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Documentation:	---	CRM:
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-07-25 10:07:24 UTC

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

smb: client: harden POSIX SID length parsing

posix_info_sid_size() reads sid[1] to obtain the subauthority count,
but its existing boundary check still accepts buffers with only one
remaining byte. Require two bytes before reading sid[1] so all client
paths that reuse the helper reject truncated POSIX SIDs safely.

Comment 1 TEJ RATHI 2026-07-29 16:14:12 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026072525-CVE-2026-64380-95d8@gregkh/T