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Libsoup CVE-2026-66339

| EUVDEUVD-2026-48751 MEDIUM
Insertion of Sensitive Information Into Sent Data (CWE-201)
2026-07-24 secalert@redhat.com GHSA-vh9q-f797-xwg7
Information Disclosure Red Hat Enterprise Linux Libsoup Gnome
6.5
CVSS 3.1 · Vendor: redhat
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Vulnerability Assessment

Weakness
CWE
CWE-201
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V14 - Data Protection Outbound data filtering
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Jul 26, 2026

libsoup leaks proxy credentials to destination servers via Proxy-Authorization header attachment after CONNECT tunnel establishment. Affects libsoup when used with HTTP proxies for HTTPS tunneling. No public exploit is known, and exploitation probability is low (EPSS 0.23%).

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  • Exploit and PoC references, threat intelligence from 22 sources
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Severity by source

Vendor (redhat) PRIMARY 6.5 MEDIUM
AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
SUSE MEDIUM
Red Hat 6.5 MEDIUM

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

DescriptionCVE.org

A flaw was found in libsoup. After a CONNECT tunnel is established through an HTTP proxy, libsoup incorrectly attaches the Proxy-Authorization header to subsequent HTTPS requests sent through that tunnel to the destination server. This allows the destination server to capture proxy credentials, leading to information disclosure.

Threat Intelligence Overview

EPSS Score
0.2%
Top 86% exploitable
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment MSRC Vendor VulDB

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity MEDIUM
CISA KEV No
Public POC No
EPSS 0.2%
Patch available Yes
Active threat No
Deciding rule
MEDIUM severity (CVSS 4.0-6.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact· derived
Medium
Technical Impact
Partial

Priority Score

32
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +32
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)CVE.org

cpe:2.3:a:gnome:libsoup:-:*:*:*:*:*:*:*
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:*:*:*:*:*:*:*

More in Libsoup

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9.8 Oct 06

libsoup from versions 2.65.1 until 2.68.1 have a heap-based buffer over-read because soup_ntlm_parse_challenge() in soup
CVE-2024-52530 HIGH POC
7.5 Nov 11

GNOME libsoup before 3.6.0 allows HTTP request smuggling in some configurations because '\0' characters at the end of he
CVE-2025-2784 MEDIUM POC
6.5 Apr 03

A flaw was found in libsoup. Rated high severity (CVSS 7.0), this vulnerability is remotely exploitable, no authenticati
CVE-2024-52531 MEDIUM POC
6.5 Nov 11

GNOME libsoup before 3.6.1 allows a buffer overflow in applications that perform conversion to UTF-8 in soup_header_pars
CVE-2026-102560 CRITICAL
9.8 Sep 29

A heap buffer overflow exists in libsoup's WebSocket permessage-deflate compression path: when a very large outbound mes
CVE-2026-1536 MEDIUM POC
5.8 Jan 28

HTTP header injection in libsoup through CRLF sequences in the Content-Disposition header allows unauthenticated remote

CVE-2026-1467 MEDIUM POC
5.8 Jan 27

libsoup's improper handling of URL-decoded input in HTTP proxy configurations allows remote attackers to inject CRLF seq
CVE-2018-12910 CRITICAL
9.8 Jul 05

The get_cookies function in soup-cookie-jar.c in libsoup 2.63.2 allows attackers to have unspecified impact via an empty
CVE-2026-102559 HIGH
8.6 Sep 29

Heap memory corruption in libsoup can be triggered when a WebSocket client using libsoup constructs a masked outgoing fr
CVE-2026-102558 HIGH
8.6 Sep 29

Heap out-of-bounds read in libsoup's WebSocket implementation allows a remote, unauthenticated peer to trigger a heap bu
CVE-2026-102557 HIGH
8.6 Sep 29

Heap corruption and denial of service in libsoup stem from unbounded WebSocket message reassembly: the code accumulates

CVE-2026-102556 HIGH
8.6 Sep 29

A type-confusion memory-safety flaw in libsoup's WebSocket handling can crash or corrupt the heap of applications that p

Same weakness CWE-201 – Insertion of Sensitive Information Into Sent Data

View all
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7.5
CVE-2025-58098 HIGH POC
8.3
CVE-2024-43283 MEDIUM POC
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CVE-2026-105849 HIGH POC
7.7
CVE-2020-37150 HIGH POC
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Same technique Information Disclosure

View all
CVE-2019-2725 CRITICAL POC
9.8
CVE-2021-34523 CRITICAL POC
9.0
CVE-2013-2251 CRITICAL POC
9.8
CVE-2017-5638 CRITICAL POC
9.8
CVE-2025-24813 CRITICAL POC
9.8
CVE-2025-68613 HIGH POC
8.8
CVE-2015-1701 HIGH POC
7.8
CVE-2017-0147 HIGH POC
7.5

Vendor StatusVendor

SUSE

Severity: Moderate
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Micro 5.3 Affected

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-66339 ADVISORY https://ubuntu.com/security/notices/USN-8890-1 ADVISORY https://vuldb.com/vuln/383031 REF https://access.redhat.com/security/cve/CVE-2026-66339 REF https://bugzilla.redhat.com/show_bug.cgi?id=2506951

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