CVE-2026-89536: SUNRPC: wait for in-flight client TLS handshake callback

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.6%

EPSS score, percentile 50.3 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

9.8 Critical

CVSS v3.1 base score, given by the CNA

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected

• 6.5

Unaffected before 6.5; 6.6.157; 6.12.109; 6.18.50; 7.2.4; 7.3

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Versions not listed are: unaffected.

Versions not listed are: affected.

Versions the record lists as unaffected: 6.6.157, 6.12.109, 6.18.50, 7.2.4, 7.3.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

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…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-89536 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 11 Sep 2026.
• The CVE record carries a CVSS v3.1 base score of 9.8 (Critical), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.6% (percentile 50.3), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

SUNRPC: wait for in-flight client TLS handshake callback

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.

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline

Known exploited Linux vulnerabilities

• CVE-2026-46300: Linux Kernel Missing Initialization of a Variable Vulnerability (added 28 Oct 2026)
• CVE-2025-39682: Linux Kernel Improper Check for Unusual or Exceptional Conditions Vulnerability (added 18 Sep 2026)
• CVE-2025-39964: Linux Kernel Race Condition Vulnerability (added 18 Sep 2026)
• CVE-2026-53266: Linux Kernel Out-of-Bounds Write Vulnerability (added 18 Sep 2026)
• CVE-2026-53362: Linux Kernel Unspecified Vulnerability (added 27 Aug 2026)