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CVE-2026-66338 Details

Description

A flaw was found in libsoup. The chunked transfer encoding parser uses a permissive parsing function for chunk sizes that silently accepts inputs violating RFC 9112, including leading whitespace, plus sign prefixes, and trailing invalid characters. When libsoup operates behind a strict frontend proxy, this parsing differential can be exploited to smuggle HTTP requests.

Metrics

CVSS 3.x Severity and Vector Strings:

NIST: [email protected]CVSS-B:7.2 HIGHVector:CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

CNA: [email protected]CVSS-B:5.4 MEDIUMVector:CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N

References to Advisories, Solutions, and Tools

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URL	Source(s)	Tag(s)
https://access.redhat.com/security/cve/CVE-2026-66338	[email protected]	Vendor Advisory
https://bugzilla.redhat.com/show_bug.cgi?id=2506950	[email protected]	ExploitIssue TrackingVendor Advisory

Weakness Enumeration

CWE-ID	CWE Name	Source
CWE-444	Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')	[email protected]

Affected Products

Product	Versions
gnome libsoup	All versions
CPE cpe:2.3:a:gnome:libsoup:-:::::::* Remediation No remediation found in references.
redhat enterprise linux	6.0 7.0 8.0 9.0 10.0
CPE cpe:2.3:o:redhat:enterprise_linux:6.0:::::::* cpe:2.3:o:redhat:enterprise_linux:7.0:::::::* cpe:2.3:o:redhat:enterprise_linux:8.0:::::::* cpe:2.3:o:redhat:enterprise_linux:9.0:::::::* cpe:2.3:o:redhat:enterprise_linux:10.0:::::::* Remediation No remediation found in references.

Change History

3 change records found show changes

Date	Action	Recorded By
Aug 24, 2026	Initial Analysis	[email protected]
Jul 27, 2026	CVE Modified	CISA-ADP
Jul 24, 2026	New CVE Received	[email protected]