CVE-2026-85534
Libsoup: libsoup: http/2 client crash in on_data_source_read_callback when settings initial_window_size shrinks during deferred body read
CVSS Score
5.9
EPSS Score
0.0%
EPSS Percentile
0th
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.
| CWE | CWE-617 |
| Vendor | red hat |
| Product | red hat enterprise linux 10 |
| Published | Sep 4, 2026 |
| Last Updated | Sep 4, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Attack Vector
Network
Attack Complexity
High
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
Affected Versions
Red Hat / Red Hat Enterprise Linux 10
All versions affected Red Hat / Red Hat Enterprise Linux 6
All versions affected Red Hat / Red Hat Enterprise Linux 7
All versions affected Red Hat / Red Hat Enterprise Linux 8
All versions affected Red Hat / Red Hat Enterprise Linux 9
All versions affected References
access.redhat.com: https://access.redhat.com/security/cve/CVE-2026-85534 bugzilla.redhat.com: https://bugzilla.redhat.com/show_bug.cgi?id=2528440 gitlab.gnome.org: https://gitlab.gnome.org/GNOME/libsoup/-/blob/master/libsoup/http2/soup-client-message-io-http2.c gitlab.gnome.org: https://gitlab.gnome.org/GNOME/libsoup/-/work_items/551
Credits
Red Hat would like to thank xtromera for reporting this issue.