HTTP/2 Input Stream Buffering Flaw in libsoup by GNOME
CVE-2026-85534

5.9MEDIUM

Key Information:

Vendor

Red Hat
Status
Red Hat Enterprise Linux 10
Red Hat Enterprise Linux 6
Red Hat Enterprise Linux 7
Red Hat Enterprise Linux 8
Vendor
CVE Published:
4 September 2026

What is CVE-2026-85534?

A vulnerability exists in libsoup that stems from an improper handling of HTTP/2 request bodies sourced from non-pollable input streams. This flaw allows a malicious HTTP/2 server to manipulate the SETTINGS_INITIAL_WINDOW_SIZE while a buffered read is still being processed. Consequently, the client may attempt to copy an excessively large buffer into a smaller DATA callback without a sufficient runtime bounds check. This situation can lead to unforeseen application behavior, potentially resulting in process termination or HTTP/2 session failures. Users are encouraged to assess their environment and apply relevant updates to safeguard against this issue.

References

https://access.redhat.com/security/cve/CVE-2026-85534
vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2528440
issue-trackingx_refsource_REDHAT
https://gitlab.gnome.org/GNOME/libsoup/-/blob/master/libs...

CVSS V3.1

Score:
5.9
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Red Hat would like to thank xtromera for reporting this issue.
.