# CVE-2026-15779: Samba-winbind: samba: pam_winbind mkhomedir chowns critical system paths without validation

Status: published. Published: 2026-07-15. Updated: 2026-11-05.

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.

## Remediation

- workaround: 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. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (samba-winbind): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (samba-winbind): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (samba-winbind): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (samba-winbind): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (samba-winbind): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 6.1 (medium); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H; source: CNA: redhat

- CVSS 3.1: 6.1 (medium); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H; source: NVD: secalert@redhat.com

- CISA KEV: No listing in collected sources

- EPSS: 0.15% as of 2026-11-05; percentile 4.06%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-732

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://access.redhat.com/security/cve/CVE-2026-15779 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2499991 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://gitlab.com/samba-team/samba/-/blob/samba-4.19.4/nsswitch/pam_winbind.c (CNA: redhat)

- https://gitlab.com/samba-team/samba/-/blob/samba-4.23.5/nsswitch/pam_winbind.c#L1622 (CNA: redhat)

- https://gitlab.com/samba-team/samba/-/blob/samba-4.24.3/nsswitch/pam_winbind.c#L1590 (CNA: redhat)

- https://access.redhat.com/security/cve/CVE-2026-15779 (secalert@redhat.com)

- https://bugzilla.redhat.com/show_bug.cgi?id=2499991 (secalert@redhat.com)

- https://gitlab.com/samba-team/samba/-/blob/samba-4.19.4/nsswitch/pam_winbind.c (secalert@redhat.com)

- https://gitlab.com/samba-team/samba/-/blob/samba-4.23.5/nsswitch/pam_winbind.c#L1622 (secalert@redhat.com)

- https://gitlab.com/samba-team/samba/-/blob/samba-4.24.3/nsswitch/pam_winbind.c#L1590 (secalert@redhat.com)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-15779; retrieved 2026-11-05; source updated 2026-11-05

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-15779; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-15779; retrieved 2026-11-05; source updated Not reported

Revision: 0843d976829a5ad3f07294504ceff7656d965c5bc6877a377c900ba25ae591f5

Canonical: https://y2.dev/cve/CVE-2026-15779

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