CVE-2026-31533

Status: ModifiedCritical (9.8)—

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.

Read full descriptionShow less

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

Version: 3.1
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Base score: 9.8

Exploitation probability (EPSS)

Probability of exploitation in the next 30 days: 0.71%
Percentile among all scored CVEs: 52
Score date: 10/6/2026

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

ExploitationT1190 Exploit Public-Facing Applicationinitial access75 %
Primary impactT1059 Command and Scripting Interpreterexecution70 %

Vulnerabilidad remota crítica (CVSS 3.1 AV:N) en Linux kernel que permite uso de memoria después de liberación (CWE-416) en TLS. Explotable por red sin privilegios. Impacto: ejecución de código mediante corrupción de memoria en el contexto del kernel.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Privileged Account Management Vulnerability Scanning Restrict Web-Based Content Network Segmentation Limit Software Installation Limit Access to Resource Over Network

Affected technologies (1)

Linux — Linux Kernel

CWEs

CWE-416

References

Raw JSON (NVD)

Show

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      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet/tls: fix use-after-free in -EBUSY error path of tls_do_encryption\n\nThe -EBUSY handling in tls_do_encryption(), introduced by commit\n859054147318 (\"net: tls: handle backlogging of crypto requests\"), has\na use-after-free due to double cleanup of encrypt_pending and the\nscatterlist entry.\n\nWhen crypto_aead_encrypt() returns -EBUSY, the request is enqueued to\nthe cryptd backlog and the async callback tls_encrypt_done() will be\ninvoked upon completion. That callback unconditionally restores the\nscatterlist entry (sge->offset, sge->length) and decrements\nctx->encrypt_pending. However, if tls_encrypt_async_wait() returns an\nerror, the synchronous error path in tls_do_encryption() performs the\nsame cleanup again, double-decrementing encrypt_pending and\ndouble-restoring the scatterlist.\n\nThe double-decrement corrupts the encrypt_pending sentinel (initialized\nto 1), making tls_encrypt_async_wait() permanently skip the wait for\npending async callbacks. A subsequent sendmsg can then free the\ntls_rec via bpf_exec_tx_verdict() while a cryptd callback is still\npending, resulting in a use-after-free when the callback fires on the\nfreed record.\n\nFix this by skipping the synchronous cleanup when the -EBUSY async\nwait returns an error, since the callback has already handled\nencrypt_pending and sge restoration."
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