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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
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.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-72151 being exploited?
There is no known exploitation of CVE-2026-72151 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72151, DEBIAN-CVE-2026-72151, GHSA-53hq-7c43-pvmj, UBUNTU-CVE-2026-72151.