# CVE-2026-98845: tpm: Disable TPM on null key name mismatch

> A Linux kernel TPM driver flaw fails to disable the chip on null key mismatch, allowing attackers to bypass TPM reset attack protections.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** BELL-CVE-2026-98845, DEBIAN-CVE-2026-98845, GHSA-g3p5-hgwr-rqx7, UBUNTU-CVE-2026-98845

## What is CVE-2026-98845?

CVE-2026-98845 is a vulnerability in Linux, published on 18 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In the Linux kernel, the following vulnerability has been resolved:

tpm: Disable TPM on null key name mismatch

The null key name check exists to protect against TPM reset attacks, so
a mismatch should stop the device from serving further requests.
Currently it does not disable the chip when it finds a mismatch.

The mismatch is logged:

    tpm tpm0: null key integrity check failed

but the chip keeps serving commands:

    / # tpm2_getcap -c properties-fixed
    TPM_PT_FAMILY_INDICATOR:
      as UINT32:                0x08322e3000
      as string:                "2.0"
    ...

tpm2_load_null() where the null key name check is run sets the chip as
disabled only if the rc is non zero. When the mismatch is seen, rc is
zero at that point and it returns success. The other issue is that the
caller expects the null key handle to be populated when the function
returns 0 which it does here without writing the handle and proceeds
assuming the null key handle is valid.

During the test, I noticed that tpm2_start_auth_session() uses the
uninitialized stack value as the key handle since tpm2_load_null()
returns 0 despite the integrity failure and proceeds with
TPM2_CC_START_AUTH_SESS with this value as salt key handle.

Set rc to -ENODEV on the mismatch. The error path then disables the chip
and returns the correct code to the caller.

Tested in QEMU with swtpm and CONFIG_TCG_TPM2_HMAC=y by making
TPM2_CC_CONTEXT_LOAD fail with TPM2_RC_INTEGRITY and changing the name
of the re-created null key. The chip is now disabled on the mismatch.

## Which versions are affected by CVE-2026-98845?


## How do I fix CVE-2026-98845?

Apply the vendor's patch.

## Is CVE-2026-98845 being exploited?

There is no known exploitation of CVE-2026-98845 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98845 and fix it if it is affected.

What it is: CVE-2026-98845 is a vulnerability in Linux, published on 18 Oct 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-2026-98845 in the wild and no public exploit code.

Affected product: Linux. 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-2026-98845/ (Markdown: https://insights.sbomify.com/CVE-2026-98845/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98845
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98845
- OSV: https://osv.dev/vulnerability/CVE-2026-98845

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98845/
Summaries are generated and may contain mistakes; the official description above is the record.