Sandboxed-containers: kernel: systemd-gpt-auto-generator: guest data leakage in confidential computing (sandboxed containers)
Summary
| CVE | CVE-2026-121876 |
|---|---|
| State | PUBLISHED |
| Assigner | redhat |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-11-12 17:17:29 UTC |
| Updated | 2026-11-12 17:17:29 UTC |
| Description | A flaw was found in the interaction between systemd-gpt-auto-generator and confidential computing guest VM images in OpenShift Sandboxed Containers (confidential peer pods). systemd-gpt-auto-generator automatically discovers and mounts GPT partitions by type GUID at boot with no user confirmation. In the confidential computing threat model, where the host/hypervisor is the adversary, a malicious host can inject partitions into the guest's virtual disk. Most critically, injecting a swap partition causes the guest kernel to page out TEE-encrypted memory to a host-controlled block device, breaking the confidentiality guarantee of the hardware TEE (AMD SEV-SNP, Intel TDX). The PodVM images use a GPT-partitioned disk with dm-verity on the root partition. However, the roothash= kernel parameter only disables root auto-discovery — non-root partitions (swap, /home, /var, /srv, /var/tmp) are still auto-discovered and mounted. The generator is shipped unmasked in the RHEL systemd-udev subpackage, and no kernel command line parameter in the measured UKI addon disables it. Additionally, the PodVM measurement script captures PCRs 3, 9, 11, and 12, but not PCR 5 (GPT partition table), so partition table modifications are not detected by remote attestation. |
Risk And Classification
Primary CVSS: v3.1 7.9 HIGH from [email protected]
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N
Problem Types: CWE-359 | CWE-359 Exposure of Private Personal Information to an Unauthorized Actor
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 7.9 | HIGH | CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N |
| 3.1 | CNA | CVSS | 7.9 | HIGH | CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N |
CVSS v3.1 Breakdown
CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| 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 7 | Not specified | Not specified |
| CNA | Red Hat | Red Hat Enterprise Linux 8 | 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 |
| CNA | Red Hat | Red Hat Enterprise Linux 9 | Not specified | Not specified |
| CNA | Red Hat | Red Hat OpenShift Container Platform 4 | Not specified | Not specified |
| CNA | Red Hat | Red Hat OpenShift Container Platform 4 | Not specified | Not specified |
| CNA | Red Hat | Red Hat OpenShift Container Platform 5 | Not specified | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| bugzilla.redhat.com/show_bug.cgi | [email protected] | bugzilla.redhat.com | |
| access.redhat.com/security/cve/CVE-2026-121876 | [email protected] | access.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: Red Hat would like to thank Spyros Seimenis (Edgeless Systems) for reporting this issue. (en)
Additional Advisory Data
| Source | Time | Event |
|---|---|---|
| CNA | 2026-10-16T00:00:00.000Z | Reported to Red Hat. |
| CNA | 2026-11-12T14:00:00.000Z | Made public. |
Workarounds
CNA: Add systemd.gpt_auto=0 to the measured kernel command line (UKI addon) to completely disable systemd-gpt-auto-generator. Since the PodVM already uses explicit partition layout and dm-verity, auto-discovery is unnecessary. Alternative mitigations: - Disable swap specifically: add systemd.swap=0 to the kernel command line - Mask the generator in the guest image: ln -sf /dev/null /etc/systemd/system-generators/systemd-gpt-auto-generator - Include PCR 5 in the PodVM measurement script alongside PCRs 3, 9, 11, 12 - For systemd 254+: set restrictive image policy via systemd.image_policy=root=verity+signed+encrypted+unprotected+absent:swap=absent:home=absent:srv=absent:var=absent:tmp=absent