Amazon Linux 2023 : libsoup3, libsoup3-devel (ALAS2023-2026-3240)

high Nessus Plugin ID 371834

Synopsis

The remote Amazon Linux 2023 host is missing a security update.

Description

It is, therefore, affected by multiple vulnerabilities as referenced in the ALAS2023-2026-3240 advisory.

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. (CVE-2026-103399)

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. (CVE-2026-66337)

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. (CVE-2026-66338)

Tenable has extracted the preceding description block directly from the tested product security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Run 'dnf update libsoup3 --releasever 2023.12.20261026' or or 'dnf update --advisory ALAS2023-2026-3240 --releasever 2023.12.20261026' to update your system.

Plugin Details

Severity: High

ID: 371834

File Name: al2023_ALAS2023-2026-3240.nasl

Version: 1.1

Type: Local

Agent: unix

Family: Amazon Linux Local Security Checks

Published: 10/25/2026

Updated: 10/25/2026

Supported Sensors: Agentless Assessment, Continuous Assessment, Frictionless Assessment Agent, Frictionless Assessment AWS, Nessus Agent, Tenable Cloud Security, Tenable Self-Hosted Container Security, Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.3

Percentile: 53.51

CVSS v2

Risk Factor: Medium

Base Score: 6.4

Temporal Score: 5

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:N

CVSS Score Source: CVE-2026-66338

CVSS v3

Risk Factor: High

Base Score: 7.2

Temporal Score: 6.5

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:amazon:linux:2023, p-cpe:/a:amazon:linux:libsoup3-debuginfo, p-cpe:/a:amazon:linux:libsoup3-debugsource, p-cpe:/a:amazon:linux:libsoup3-devel, p-cpe:/a:amazon:linux:libsoup3-doc, p-cpe:/a:amazon:linux:libsoup3

Required KB Items: Host/local_checks_enabled, Host/AmazonLinux/release, Host/AmazonLinux/rpm-list

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 10/24/2026

Vulnerability Publication Date: 7/24/2026

Reference Information

CVE: CVE-2026-103399, CVE-2026-66337, CVE-2026-66338

IAVA: 2026-A-1151

Detections

Analytics