# CVE-2026-72151: tpm: tpm2-sessions: wait for async KPP completion in tpm_buf_append_salt

> A use-after-free in the Linux kernel TPM driver occurs when asynchronous KPP operations complete after the request is freed, causing a kernel crash.

- **Severity:** High 8.4 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **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:** 15 Aug 2026
- **Updated:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-72151, DEBIAN-CVE-2026-72151, GHSA-53hq-7c43-pvmj, UBUNTU-CVE-2026-72151

## What is CVE-2026-72151?

CVE-2026-72151 is a high-severity use after free vulnerability in Linux, published on 15 Aug 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: tpm2-sessions: wait for async KPP completion in tpm_buf_append_salt

tpm_buf_append_salt() in drivers/char/tpm/tpm2-sessions.c calls
crypto_kpp_generate_public_key() and crypto_kpp_compute_shared_secret()
without installing a completion callback, discards both return values,
and immediately frees the kpp_request via kpp_request_free(). When the
resolved ecdh-nist-p256 KPP backend is asynchronous (atmel-ecc, HPRE,
keembay-ocs), either operation returns -EINPROGRESS and the deferred
completion worker dereferences the freed request.

The path fires automatically from the hwrng_fillfn kernel thread via
tpm_get_random -> tpm2_get_random -> tpm2_start_auth_session ->
tpm_buf_append_salt on every entropy poll, without any userland action.

Install crypto_req_done as the completion callback, wrap both KPP
operations in crypto_wait_req(), and propagate errors to the caller.
The wait is a no-op for synchronous backends.

## Which versions are affected by CVE-2026-72151?


## How do I fix CVE-2026-72151?

Apply the vendor's patch.

## Is CVE-2026-72151 being exploited?

There is no known exploitation of CVE-2026-72151 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-72151 and fix it if it is affected.

What it is: CVE-2026-72151 is a high-severity use after free vulnerability in Linux, published on 15 Aug 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-2026-72151 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-2026-72151/ (Markdown: https://insights.sbomify.com/CVE-2026-72151/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-72151
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-72151
- OSV: https://osv.dev/vulnerability/CVE-2026-72151

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-72151/
Summaries are generated and may contain mistakes; the official description above is the record.