CVE-2026-5398: Kernel use-after-free bug in the TIOCNOTTY handler

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?

0.2%

EPSS score, percentile 10.9 of all scored records. A probability estimated by FIRST, not a report of exploitation.

How severe?

8.4 High

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

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

Advisories and patches (1)

Which versions are affected?

Affected

• from 15.0-RELEASE to before p6
• from 14.4-RELEASE to before p2
• from 14.3-RELEASE to before p11
• from 13.5-RELEASE to before p12

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

• security.freebsd.org (Vendor advisory)

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: unknown.

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

About this vulnerability

The implementation of TIOCNOTTY failed to clear a back-pointer from the structure representing the controlling terminal to the calling process' session. If the invoking process then exits, the terminal structure may end up containing a pointer to freed memory. A malicious process can abuse the dangling pointer to grant itself root privileges.

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-5398 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 22 Apr 2026.
• The CVE record carries a CVSS v3.1 base score of 8.4 (High), taken from CISA's enrichment of the record.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.2% (percentile 10.9), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation none, automatable no, technical impact total.
• The credits in the CVE record name Anthropic (Claude) as finder.

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

Kernel use-after-free bug in the TIOCNOTTY handler

The implementation of TIOCNOTTY failed to clear a back-pointer from the structure representing the controlling terminal to the calling process' session. If the invoking process then exits, the terminal structure may end up containing a pointer to freed memory. A malicious process can abuse the dangling pointer to grant itself root privileges.

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

Timeline