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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

Published: Sep 4, 2026Updated: Sep 4, 2026 Sources: CVE List NVDCWE-617
5.9MEDIUM
NVD MITRE
EPSS Score
0.3%
Top 75.9%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Workaround Only
Self-Check
Not available

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.

No summary for this CVE yet.

CVSS Vector Breakdown

AV:NAC:HPR:NUI:NS:UC:NI:NA:H
Exploitability
AV:NAttack Vector
Network
AC:HAttack Complexity
High
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:NIntegrity
None
A:HAvailability
High
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Weaknesses

CWE-617

Affected Products

Red Hat
commercial·US
Red Hat Enterprise Linux 10On-premOS
Operating Systems / linux-distro
and 4 more affected products View all →

Exploitability

Workaround Available

Attack Graph

Products CVE Techniques Tactics

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MITRE ATT&CK

1 technique
Impact
View detailed technique mapping

References

https://access.redhat.com/security/cve/CVE-2026-85534
access.redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2528440
bugzilla.redhat.com
https://gitlab.gnome.org/GNOME/libsoup/-/blob/master/libsoup/http2/soup-client-message-io-http2.c
gitlab.gnome.org
and 1 more references View all →

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