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Samba pam_winbind CVE-2026-15779

| EUVDEUVD-2026-44662 MEDIUM
Incorrect Permission Assignment for Critical Resource (CWE-732)
2026-07-15 redhat GHSA-6fmw-7w5g-3pf9
Privilege Escalation Denial Of Service Red Hat Red Hat Enterprise Linux 10 Red Hat Enterprise Linux 6 Red Hat Enterprise Linux 7 Red Hat Enterprise Linux 8 Red Hat Enterprise Linux 9 Suse Red Hat
6.1
CVSS 3.1 · Vendor: redhat
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Severity by source

Vendor (redhat) PRIMARY
6.1 MEDIUM
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
vuln.today AI
6.1 MEDIUM

Local vector confirmed by description; PR:L because sudo delegation (not root) suffices; A:H for catastrophic availability loss; I:L for ownership metadata change without write access.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
4.0 AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N
SUSE
MEDIUM
qualitative
Red Hat
6.1 MEDIUM
qualitative

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

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

Lifecycle Timeline

2
Analysis Generated
Jul 15, 2026 - 13:24 vuln.today
CVE Published
Jul 15, 2026 - 12:33 nvd
MEDIUM 6.1

DescriptionCVE.org

A 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.

AnalysisAI

Unvalidated chown in Samba's pam_winbind module allows a local user with narrow sudo delegation to transfer ownership of the root filesystem directory to a system account, causing system-wide denial of service on Red Hat Enterprise Linux 6 through 10. When mkhomedir is enabled and a system account has its home directory set to '/', any PAM-triggered authentication event run as that account via sudo invokes the chown without path sanitization. The resulting ownership change breaks SSH, sudo, and package-manager functionality, though the 0555 permissions on RHEL prevent write access escalation, confining the impact to high-severity availability loss. No public exploit or CISA KEV listing is identified at time of analysis.

Technical ContextAI

pam_winbind is a PAM (Pluggable Authentication Module) component of Samba that integrates Linux authentication with Windows Active Directory environments through the Winbind daemon. The 'mkhomedir' feature within pam_winbind creates a user's home directory on first login by calling chown to assign ownership to the authenticating account. The vulnerable code path in nsswitch/pam_winbind.c (referenced at samba-4.23.5 line 1622 and samba-4.24.3 line 1590) performs this chown without verifying that the resolved home directory path is not a critical system location such as '/'. CWE-732 (Incorrect Permission Assignment for Critical Resource) captures the root cause precisely: a privileged filesystem operation is applied to an insufficiently validated target path, allowing ownership of a critical resource to be incorrectly reassigned. Affected CPEs span Red Hat Enterprise Linux 6 through 10, all of which ship pam_winbind as part of the samba-winbind-clients package.

RemediationAI

Consult the Red Hat Security Advisory at https://access.redhat.com/security/cve/CVE-2026-15779 for vendor-released errata packages; no exact fixed RPM version could be independently confirmed from the available input data, so treat 'patch available per vendor advisory' as the operative status pending Red Hat errata publication. As an immediate compensating control, disable the mkhomedir option in pam_winbind configuration (typically in /etc/pam.d/system-auth or /etc/security/pam_winbind.conf) if home directory auto-creation is not operationally required - this directly eliminates the code path that performs the unvalidated chown, with the trade-off that new AD users will not have home directories created automatically on first login. Additionally, audit all local system accounts for those whose home directory is set to '/' (inspect /etc/passwd and any LDAP/AD-sourced entries via 'getent passwd') and reassign home directories to safe, non-critical paths. Review sudo policies to ensure that delegations scoped to system accounts with '/' home directories do not exist; removing such delegations prevents non-root triggering of the vulnerability. If neither patching nor mkhomedir disablement is immediately feasible, restricting PAM-based AD authentication to accounts explicitly provisioned with valid home directories serves as a partial mitigation.

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Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Enterprise Storage 7.1 Affected
SUSE Linux Enterprise High Availability Extension 12 SP5 Affected
SUSE Linux Enterprise High Availability Extension 15 SP4 Affected
SUSE Linux Enterprise High Availability Extension 15 SP5 Affected
SUSE Linux Enterprise High Availability Extension 15 SP6 Affected

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CVE-2026-15779 vulnerability details – vuln.today
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