Bug 2506949 (CVE-2026-66337)

Summary:	CVE-2026-66337 libsoup: libsoup: Heap buffer over-read via integer underflow in soup_filter_input_stream_read_until()
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in libsoup. An unsigned integer underflow in the soup_filter_input_stream_read_until() function causes a heap buffer over-read when parsing multipart HTTP responses. A malicious HTTP server can exploit this by sending a crafted multipart response, potentially causing the client application to crash or disclose sensitive heap memory.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-07-24 22:29:33 UTC

An unsigned integer underflow in soup_filter_input_stream_read_until() in libsoup/soup-filter-input-stream.c causes a heap buffer over-read when parsing multipart HTTP responses. When include_boundary is FALSE and the internal buffer contains fewer bytes than the boundary string length, the subtraction of two unsigned values wraps to a very large number, causing the boundary scan loop to read beyond the heap allocation. A malicious HTTP server can trigger this against any libsoup client using SoupMultipartInputStream. This is related to but distinct from CVE-2026-1761 — Red Hat's downstream fix for that CVE does not resolve this issue.

Upstream report: https://gitlab.gnome.org/GNOME/libsoup/-/work_items/532
PSIRTSUPT: https://redhat.atlassian.net/browse/PSIRTSUPT-17666