CVE-2026-121876
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Information Disclosure in OpenShift Sandboxed Containers

Publication date: 2026-11-12

Last updated on: 2026-11-12

Assigner: redhat-SADP

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.

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Meta Information

Published
2026-11-12
Last Modified
2026-11-12
Generated
2026-11-12
AI Q&A
2026-11-12
EPSS Evaluated
N/A
NVD
CVE-2026-121876
EUVD
EUVD-2026-124550

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-359 The product does not properly prevent a person's private, personal information from being accessed by actors who either (1) are not explicitly authorized to access the information or (2) do not have the implicit consent of the person about whom the information is collected.

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Executive Summary

This vulnerability involves systemd-gpt-auto-generator in OpenShift Sandboxed Containers. It automatically mounts GPT partitions at boot without user confirmation. In confidential computing, a malicious host can inject partitions like swap into a guest VM's disk. When swap is activated, TEE-encrypted memory is paged out to the host-controlled device, breaking confidentiality guarantees of AMD SEV-SNP or Intel TDX. Non-root partitions like /var or /home are also vulnerable to manipulation.

Detection Guidance

Check if systemd-gpt-auto-generator is active by running: systemctl status systemd-gpt-auto-generator. Inspect mounted partitions with lsblk or mount. Verify swap partition presence with swapon --show. Review kernel parameters in /proc/cmdline for roothash= or other mitigations.

Impact Analysis
  • A malicious host can read TEE-encrypted memory via swap partition injection.
  • Data capture or injection of malicious content through replacement of /var or /home mounts.
  • Exposure of LUKS auto-unlock keys via compromised vTPM.
  • Injection of modified boot configurations by replacing ESP or XBOOTLDR.
Compliance Impact

This vulnerability breaks confidentiality guarantees of hardware TEEs, which are critical for compliance with data protection regulations like GDPR and HIPAA. Exposure of encrypted memory or sensitive data to untrusted hosts violates requirements for data confidentiality and integrity.

Mitigation Strategies
  • Disable systemd-gpt-auto-generator by adding systemd.gpt_auto=0 to kernel command line.
  • Disable swap partitions in guest VMs to prevent memory paging.
  • Mask the generator in guest images using systemctl mask systemd-gpt-auto-generator.
  • Update measurement scripts to include PCR 5 for GPT partition table detection.

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