Description
A flaw was found in SoupServer (libsoup). When an HTTP/1.x client sends a request with Expect: 100-continue and a request body, and SoupServer returns an early final (non-1xx) response before the body is read, the server neither drains the declared body bytes nor closes the connection. On a keep-alive connection, those leftover bytes are interpreted as a subsequent HTTP request. A remote, unauthenticated attacker can place a complete HTTP request in the body and cause SoupServer to process that smuggled request, leading to unintended request handling.
Published: 2026-09-30
Score: 5.3 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

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Remediation

Vendor Workaround

To mitigate this do not expose SoupServer to untrusted networks; prefer terminating proxies or internal-only listeners. If SoupServer must sit behind a reverse proxy, disable backend connection reuse/pooling across clients so an undrained body cannot prepend to another client's request.

Tracking

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Advisories
Source ID Title
Ubuntu USN Ubuntu USN USN-8975-1 libsoup vulnerabilities
History

Sun, 25 Oct 2026 20:30:00 +0000

Type Values Removed Values Added
First Time appeared Red Hat
Red Hat enterprise Linux
Vendors & Products Red Hat
Red Hat enterprise Linux

Thu, 01 Oct 2026 00:15:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Wed, 30 Sep 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Wed, 30 Sep 2026 17:45:00 +0000

Type Values Removed Values Added
Description A flaw was found in SoupServer (libsoup). When an HTTP/1.x client sends a request with Expect: 100-continue and a request body, and SoupServer returns an early final (non-1xx) response before the body is read, the server neither drains the declared body bytes nor closes the connection. On a keep-alive connection, those leftover bytes are interpreted as a subsequent HTTP request. A remote, unauthenticated attacker can place a complete HTTP request in the body and cause SoupServer to process that smuggled request, leading to unintended request handling.
Title Libsoup: soupserver: http/1 request smuggling via undrained expect: 100-continue body
First Time appeared Redhat
Redhat enterprise Linux
Weaknesses CWE-444
CPEs cpe:/o:redhat:enterprise_linux:10
cpe:/o:redhat:enterprise_linux:6
cpe:/o:redhat:enterprise_linux:7
cpe:/o:redhat:enterprise_linux:8
cpe:/o:redhat:enterprise_linux:9
Vendors & Products Redhat
Redhat enterprise Linux
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N'}


Subscriptions

Red Hat Enterprise Linux
Redhat Enterprise Linux
cve-icon MITRE

Status: PUBLISHED

Assigner: redhat

Published:

Updated: 2026-11-03T02:02:18.770Z

Reserved: 2026-09-30T14:31:37.532Z

Link: CVE-2026-103399

cve-icon Vulnrichment

Updated: 2026-09-30T19:11:08.587Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2026-09-30T18:18:16.137

Modified: 2026-09-30T20:17:30.987

Link: CVE-2026-103399

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-09-29T00:00:00Z

Links: CVE-2026-103399 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-25T19:15:16Z

Weaknesses