# CVE-2026-121876: Security feature bypass in Red Hat Enterprise Linux 10

> A malicious host can inject swap partitions into confidential guest VMs, leaking TEE-encrypted memory to the host; confidential computing users should care.

- **Severity:** High 7.9 (`CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Harmful if only installed:** No
- **Needs a specific call:** No
- **Fix available:** No
- **Published:** 12 Nov 2026
- **Updated:** 12 Nov 2026
- **Also known as:** GHSA-pvr5-j3rg-w9p8

## What is CVE-2026-121876?

CVE-2026-121876 is a high-severity security feature bypass vulnerability in Red Hat Enterprise Linux 10, published on 12 Nov 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official 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.

Weakness: CWE-359 (Exposure of Private Personal Information to an Unauthorized Actor)

## Which versions are affected by CVE-2026-121876?

An affected version is exposed as installed. No special setting or call is needed.


## How do I fix CVE-2026-121876?

No fix has been published for CVE-2026-121876 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-121876 being exploited?

There is no known exploitation of CVE-2026-121876 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-121876 and fix it if it is affected.

What it is: CVE-2026-121876 is a high-severity security feature bypass vulnerability in Red Hat Enterprise Linux 10, published on 12 Nov 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-121876 in the wild and no public exploit code.
Exposure: An affected version is exposed as installed. No special setting or call is needed.

Affected product: Red Hat Enterprise Linux 10. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-121876/ (Markdown: https://insights.sbomify.com/CVE-2026-121876/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-121876
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-121876
- OSV: https://osv.dev/vulnerability/CVE-2026-121876

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-121876/
Summaries are generated and may contain mistakes; the official description above is the record.