# CVE-2026-85534

## Summary

- **CVE ID:** CVE-2026-85534
- **Severity:** MEDIUM
- **CVSS Score:** 5.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H)
- **CWE:** CWE-617
- **Published:** Sep 4, 2026
- **Last Modified:** Sep 4, 2026

## Description

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.

## Affected Products

No affected products listed.

## References

- [CNA](https://access.redhat.com/security/cve/CVE-2026-85534)
- [CNA](https://bugzilla.redhat.com/show_bug.cgi?id=2528440)
- [CNA](https://gitlab.gnome.org/GNOME/libsoup/-/blob/master/libsoup/http2/soup-client-message-io-http2.c)
- [CNA](https://gitlab.gnome.org/GNOME/libsoup/-/work_items/551)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.32%
- **EPSS Percentile:** 24.2

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-11._