In the Linux kernel, krb5 crypto routines incorrectly handle asynchronous AEAD providers. When a cryptographic operation resolves to an async AEAD instance, the routine frees the buffer while the backend worker still holds a reference, causing a use‑after‑free that can crash the kernel. This results in denial of service. The issue is due to an improper treatment of negative return values from crypto_aead_{encrypt,decrypt}(), which are considered terminal even when the return code is -EINPROGRESS. The bug is confined to the krb5 module’s encryption and decryption functions in rfc3961_simplified.c and rfc8009_aes2.c, and is triggered when an async AEAD instance is bound to the krb5 encrypt_name name.

All Linux kernel deployments that load the krb5 module with an async AEAD provider bound to the krb5 encrypt_name are affected. The vulnerability is reachable through net/rxrpc/rxgk.c, fs/afs/cm_security.c and net/ceph/crypto.c on systems where such a provider is configured.

The EPSS score is below 1%, indicating a low probability of exploitation, and the vulnerability is not listed in the CISA KEV catalog. An attacker would need to trigger a krb5 encryption/decrypt call that selects the async provider to exploit the bug. Once triggered, the kernel may crash, leading to denial of service. The risk is mitigated by promptly applying the vendor patch or removing the problematic provider.