CVE-2026-31533

Status: UPDATED  |  Advisory ID: CVE-2026-31533

Key Details

Affected Products, Subsystems & Sectors

What to Know

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

net/tls: fix use-after-free in -EBUSY error path of tls_do_encryption

The -EBUSY handling in tls_do_encryption(), introduced by commit

859054147318 ("net: tls: handle backlogging of crypto requests"), has

a use-after-free due to double cleanup of encrypt_pending and the

scatterlist entry.

When crypto_aead_encrypt() returns -EBUSY, the request is enqueued to

the cryptd backlog and the async callback tls_encrypt_done() will be

invoked upon completion. That callback unconditionally restores the

scatterlist entry (sge->offset, sge->length) and decrements

ctx->encrypt_pending. However, if tls_encrypt_async_wait() returns an

error, the synchronous error path in tls_do_encryption() performs the

same cleanup again, double-decrementing encrypt_pending and

double-restoring the scatterlist.

The double-decrement corrupts the encrypt_pending sentinel (initialized

to 1), making tls_encrypt_async_wait() permanently skip the wait for

pending async callbacks. A subsequent sendmsg can then free the

tls_rec via bpf_exec_tx_verdict() while a cryptd callback is still

pending, resulting in a use-after-free when the callback fires on the

freed record.

Fix this by skipping the synchronous cleanup when the -EBUSY async

wait returns an error, since the callback has already handled

encrypt_pending and sge restoration. (NVD)

What to Do

Monitor Siemens's web page for any future patch releases.

References