# CVE-2026-104034: Sssd: sssd: denial of service via use-after-free in kcm ticket renewal

Status: published. Published: 2026-10-06. Updated: 2026-11-05.

A flaw was found in SSSD. A use-after-free vulnerability exists in the Kerberos Credential Manager (KCM) responder during Kerberos ticket-granting ticket (TGT) renewal, where a deferred callback accesses memory that has already been released. An authenticated local user with a renewable Kerberos ticket can trigger this issue on systems configured with KCM renewal, causing the KCM responder service to crash and resulting in a Denial of Service (DoS).

## Remediation

- workaround: KCM ticket renewal, the affected feature, is disabled by default (tgt_renewal defaults to false). On systems where it has been enabled, it can be disabled to avoid the vulnerable code path:

1. Edit /etc/sssd/sssd.conf and set `tgt_renewal = false` in the `[kcm]` section.
2. Restart the SSSD KCM responder to apply the change:

systemctl restart sssd-kcm.service

Note: disabling TGT renewal means renewable Kerberos tickets stored in the KCM credential cache are no longer renewed automatically and must be re-acquired (for example, with kinit) before they expire. Restarting sssd-kcm.service briefly interrupts in-flight KCM requests. (source: CNA: redhat)

## Affected products and versions

- Red Hat / Red Hat Enterprise Linux 10 (sssd): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 6 (sssd): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 7 (sssd): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 8 (sssd): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat Enterprise Linux 9 (sssd): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-8): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 4 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat
- Red Hat / Red Hat OpenShift Container Platform 5 (openshift/ose-rhel-coreos-9): Version range not reported. Source: CNA: redhat

## Severity and prioritization

- CVSS 3.1: 4.7 (medium); CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H; source: CNA: redhat

- CVSS 3.1: 4.7 (medium); CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H; source: NVD: secalert@redhat.com

- CISA KEV: No listing in collected sources

- EPSS: 0.09% as of 2026-11-05; percentile 0.38%

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

- Weaknesses: CWE-825

## Exploit evidence

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

## References

- https://access.redhat.com/security/cve/CVE-2026-104034 (CNA: redhat; vdb-entry, x_refsource_REDHAT)

- https://bugzilla.redhat.com/show_bug.cgi?id=2479178 (CNA: redhat; issue-tracking, x_refsource_REDHAT)

- https://access.redhat.com/security/cve/CVE-2026-104034 (secalert@redhat.com)

- https://bugzilla.redhat.com/show_bug.cgi?id=2479178 (secalert@redhat.com)

## Provenance

- CNA: redhat: https://www.cve.org/CVERecord?id=CVE-2026-104034; retrieved 2026-11-05; source updated 2026-11-05

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-104034; retrieved 2026-11-05; source updated 2026-11-05

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-104034; retrieved 2026-11-05; source updated Not reported

Revision: a3fe7f41bff69a4849fdc57dcac0097ae1521838d42fcfe55592d37764d6196d

Canonical: https://y2.dev/cve/CVE-2026-104034

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