CVE intelligence

CVE-2026-85534

Vulnerability intelligence

Published Sep 4, 2026Sources checked Oct 27, 2026

5.9MEDIUMCVSS out of 10

What this means

Review the available evidence

CVE-2026-85534 and is rated Medium severity with a CVSS score of 5.9. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Ubuntu Security Notices guidance

Vendor revision: Oct 21, 2026

USN-8890-1 fixed vulnerabilities in libsoup.

Microsoft Security Response Center guidance

Vendor revision: Sep 24, 2026

Release Notes

CISA KEVNot listedBased on the latest collected catalog

EPSS0.3%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-85534?

A flaw was found in libsoup. When a client sends an HTTP/2 request body from a non-pollable input stream, the library can buffer more data than the current flow-control window later allows.

A malicious HTTP/2 server can shrink SETTINGS_INITIAL_WINDOW_SIZE while that buffered read is still in progress. The client then copies the full buffer into a smaller DATA callback without a runtime bounds check, which can abort the process or fail the HTTP/2 session.

Source: NVD