CVE-2026-87861: cross-origin reuse of a Negotiate connection

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 30 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.7%

Up from 0.3% on 24 Oct 2026.

EPSS score, percentile 52.3 of all scored records. A probability estimated by FIRST, not a report of exploitation.

CISA's SSVC assessment in the CVE record lists exploitation as poc.

How severe?

9.1 Critical

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.

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

Which versions are affected?

Affected

• 8.22.0 through 8.22.0
• 8.21.0 through 8.21.0

Versions by product

Source: CISA KEV 2026.10.30, as of 30 Oct 2026; FIRST EPSS, as of 31 Oct 2026; CVE List, as of 1 Nov 2026. About the data.

Description

cross-origin reuse of a Negotiate connection

When using ambient user credentials, an HTTP request directed to one origin may be dispatched over a connection previously authenticated via Negotiate for a different origin, leaving the request's intended credentials unused.

Source: CVE List, as of 1 Nov 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 1 Nov 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

Source: CVE List, as of 1 Nov 2026. About the data.

Timeline