---
title: "CVE-2026-89536: CVE-2026-89536"
description: "In the Linux kernel, the following vulnerability has been resolved: SUNRPC: wait for in-flight client TLS handshake callback xs_tls_handshake_sync() gives xs_tls_handshake_done() a reference to the lower transport before submitting the handshake request. On timeout or signal, the synchronous waiter drops that reference after calling tls_handshake_cancel(). handshake_req_cancel() returns false when handshake_complete() has already marked the request complete. In that case the completion callback can still be running, so dropping the callback-owned reference in the waiter can free the lower transport before xs_tls_handshake_done() stores xprt_err or drops its own reference. If cancellation loses to completion, wait until xs_tls_handshake_done() signals handshake_done and let the callback release its reference. This mirrors the server-side handshake lifetime handling and keeps the timeout or signal return value unchanged."
url: https://panop.io/threat-heartbeat/CVE-2026-89536/
---

# CVE-2026-89536 CVE-2026-89536

In the Linux kernel, the following vulnerability has been resolved: SUNRPC: wait for in-flight client TLS handshake callback xs\_tls\_handshake\_sync() gives xs\_tls\_handshake\_done() a reference to the lower transport before submitting the handshake request. On timeout or signal, the synchronous waiter drops that reference after calling tls\_handshake\_cancel(). handshake\_req\_cancel() returns false when handshake\_complete() has already marked the request complete. In that case the completion callback can still be running, so dropping the callback-owned reference in the waiter can free the lower transport before xs\_tls\_handshake\_done() stores xprt\_err or drops its own reference. If cancellation loses to completion, wait until xs\_tls\_handshake\_done() signals handshake\_done and let the callback release its reference. This mirrors the server-side handshake lifetime handling and keeps the timeout or signal return value unchanged.

CVSS base score 9.8 /10

Critical

CISA KEV

Not listed

Public exploit

None known

EPSS

0.64% chance of exploitation in 30 days

[View the NVD record ↗](https://nvd.nist.gov/vuln/detail/CVE-2026-89536)

## Details

CVSS vector

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

Published

11 September 2026

Updated

15 October 2026

## References

- [https://nvd.nist.gov/vuln/detail/CVE-2026-89536](https://nvd.nist.gov/vuln/detail/CVE-2026-89536)
- [https://git.kernel.org/stable/c/15431820f448e09f8029b670d5c82aa5917d4625](https://git.kernel.org/stable/c/15431820f448e09f8029b670d5c82aa5917d4625)
- [https://git.kernel.org/stable/c/1de391e8b94e31b45c19c16dbf315e294810c7de](https://git.kernel.org/stable/c/1de391e8b94e31b45c19c16dbf315e294810c7de)
- [https://git.kernel.org/stable/c/7fbb6d2ab0391eb8d1f1a68e6bc263ef02cea61b](https://git.kernel.org/stable/c/7fbb6d2ab0391eb8d1f1a68e6bc263ef02cea61b)
- [https://git.kernel.org/stable/c/a89dd597458848b463d284b15e42a8078beeb046](https://git.kernel.org/stable/c/a89dd597458848b463d284b15e42a8078beeb046)
- [https://git.kernel.org/stable/c/fb43997407bc17ee39bac81ab708101312e255f5](https://git.kernel.org/stable/c/fb43997407bc17ee39bac81ab708101312e255f5)

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