CVE-2026-31533: Linux Kernel use-after-free (CVSS 9.8)

Description

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.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityLow

Privileges requiredNone

User interactionNone

ScopeUnchanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

Linux Kernel≥ 5.15.160 < 5.15.203 · ≥ 6.13 < 6.18.23 · ≥ 6.1.84 < 6.1.169 · ≥ 6.19 < 6.19.13

Remediation

Fixed in

Linux Kernel≥ 5.15.203

Patch & vendor advisories

References

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-31533 being actively exploited?

CVE-2026-31533 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.71%.

How severe is CVE-2026-31533?

CVE-2026-31533 has a CVSS 3.1 base score of 9.8, rated critical. EPSS estimates a 0.71% probability of exploitation.

Which products are affected by CVE-2026-31533?

Affected products include Linux Kernel.

How do I fix CVE-2026-31533?

Upgrade affected software to a fixed version, for example Linux Kernel 5.15.203 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

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