Samba-winbind: samba: pam_winbind mkhomedir chowns critical system paths without validation

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Summary

CVECVE-2026-15779
StatePUBLISHED
Assignerredhat
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-07-15 13:17:03 UTC
Updated2026-07-15 18:20:21 UTC
DescriptionA flaw was found in samba's pam_winbind. When mkhomedir is enabled, pam_winbind chowns the target account's home directory without validating the path is not a critical system directory such as /. On affected systems, accounts with / as their home directory (a common default for system accounts) can have this triggered not only by root, but by a non-root user holding a narrow sudo delegation to run commands as that account, causing ownership of / to change and resulting in severe denial of service (SSH, sudo, and package-manager failures). The change does not grant write access to / (which ships with restrictive 0555 permissions on RHEL), so the impact is availability loss rather than further privilege escalation.

Risk And Classification

Primary CVSS: v3.1 6.1 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H

Problem Types: CWE-732 | CWE-732 Incorrect Permission Assignment for Critical Resource

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary6.1MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
3.1CNACVSS6.1MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Red Hat Red Hat Enterprise Linux 10 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 6 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 7 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 8 Not specified Not specified
CNA Red Hat Red Hat Enterprise Linux 9 Not specified Not specified

References

ReferenceSourceLinkTags
access.redhat.com/security/cve/CVE-2026-15779 [email protected] access.redhat.com
gitlab.com/samba-team/samba/-/blob/samba-4.24.3/nsswitch/pam_winbind.c [email protected] gitlab.com
gitlab.com/samba-team/samba/-/blob/samba-4.23.5/nsswitch/pam_winbind.c [email protected] gitlab.com
gitlab.com/samba-team/samba/-/blob/samba-4.19.4/nsswitch/pam_winbind.c [email protected] gitlab.com
bugzilla.redhat.com/show_bug.cgi [email protected] bugzilla.redhat.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: This issue was discovered by Runar Lundgren (Red Hat). (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-05-21T00:00:00.000ZReported to Red Hat.
CNA2026-07-14T00:00:00.000ZMade public.

Workarounds

CNA: Do not enable mkhomedir in pam_winbind.conf on systems where any account (including system accounts) may resolve to a home directory of / or another sensitive system path.

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