Bug 2543274 (CVE-2026-102558)

Summary:	CVE-2026-102558 libsoup: libsoup: Heap buffer overflow during WebSocket receive-buffer growth
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in libsoup. When max-incoming-payload-size is unlimited (0), SoupWebsocketConnection could grow its incoming GByteArray based on an attacker-controlled frame length until the length wrapped, causing a heap buffer overflow while reading frame data.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2543278, 2543279, 2543280
Bug Blocks:

Description OSIDB Bzimport 2026-09-29 16:08:07 UTC

A heap buffer overflow was found in libsoup's WebSocket incoming receive buffer handling.

Incoming frames are accumulated in a GByteArray. With max-incoming-payload-size set to 0 (unlimited), a peer could declare a multi-GiB payload and stream it until the buffer length wrapped in g_byte_array_set_size() while the read still targeted the original offset, writing past the allocation.

Fixed by rejecting payload lengths above what the receive buffer can represent as soon as the frame header is parsed, before buffering the payload (commit 381a474f, libsoup 3.7.3). Such frames are closed as SOUP_WEBSOCKET_CLOSE_TOO_BIG.

References:
https://gitlab.gnome.org/GNOME/libsoup/-/work_items/554 (Bug 6)
https://gitlab.gnome.org/GNOME/libsoup/-/commit/381a474f