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libsoup CVE-2026-66337

| EUVDEUVD-2026-48753 MEDIUM
Out-of-bounds Read (CWE-125)
2026-07-24 secalert@redhat.com GHSA-ww4c-c3rv-f96h
Buffer Overflow Information Disclosure Red Hat Enterprise Linux Libsoup Gnome
6.5
CVSS 3.1 · Vendor: redhat
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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain

  1. Access
    Set up malicious HTTP server
  2. Delivery
    Client connects and requests resource
  3. Exploit
    Server sends crafted multipart HTTP response
  4. Execution
    libsoup parses response in soup_filter_input_stream_read_until()
  5. Persist
    Integer underflow causes heap buffer over-read
  6. Impact
    Client crashes or leaks heap memory

Vulnerability Assessment

Weakness
CWE
CWE-125
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, read limits
MITRE ATT&CK

1 technique across 1 tactic: Collection

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

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Exploitation Conditions

No special conditions - remote, unauthenticated exploitation is possible when a libsoup-based HTTP client processes a multipart response from a malicious server. The client application must use libsoup's multipart parsing functions, which is the default for many GNOME/GTK applications.
Impact

CVSS 6.5 (Medium) with a network attack vector, low complexity, no privileges or user interaction, and low impact to confidentiality and availability. However, EPSS score is only 0.23% (14th percentile), suggesting a very low probability of real-world exploitation. CISA KEV does not list this vulnerability, and no proof-of-concept code or active exploitation has been reported. The risk is moderate for client-side information disclosure or denial of service but is tempered by the low exploitation likelihood and the requirement that a victim client connect to a malicious server.
Exploit ScenarioDerived

A user browses to a malicious HTTP server or an application using libsoup connects to an attacker-controlled API. The server responds with a carefully crafted multipart payload, triggering the underflow. The client application then crashes or leaks portions of its heap memory.
This Month Plan within 30 days. Why: MEDIUM severity (CVSS 4.0-6.9).
No patch listed yet 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Jul 26, 2026

Heap buffer over-read in libsoup's multipart response parser allows remote, unauthenticated attackers to crash client applications or leak heap memory. The flaw occurs when processing crafted HTTP multipart responses from a malicious server. No active exploitation or public exploit code is known, and EPSS indicates low exploitation probability.

RemediationAI

Upgrade to a patched version of libsoup once released. No fixed version is specified; monitor the Red Hat advisory at https://access.redhat.com/security/cve/CVE-2026-66337 for updates. As a temporary workaround, avoid connecting to untrusted HTTP servers using software linked against libsoup, though this is impractical for general-purpose clients. Disabling multipart response parsing, if configurable, may break functionality.

Affects your stack

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Technical ContextAI · show details

libsoup is an HTTP client/server library part of the GNOME project, commonly used by Linux desktop applications. The vulnerability lies in the soup_filter_input_stream_read_until() function, which handles multipart boundary scanning. An unsigned integer underflow leads to a heap buffer over-read (CWE-125), where the parser reads beyond the buffer while searching for a boundary delimiter. No CPE strings were provided, but affected are libsoup versions that include the multipart parsing code.

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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:N/S:U/C:L/I:N/A:L
vuln.today AI 6.5 MEDIUM

Remote attack with low complexity; no privileges needed; limited information disclosure and crash impact.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N
SUSE 8.2 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Red Hat 6.5 MEDIUM

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

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

DescriptionCVE.org

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.

Threat Intelligence Overview

EPSS Score
0.2%
Top 86% exploitable
Prevalence
High
core HTTP library for GNOME desktop applications
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 No
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
Yes
Human Impact· derived
High
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

Buffer Overflow HIGH

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

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:*:*:*:*:*:*:*

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Same weakness CWE-125 – Out-of-bounds Read

View all
CVE-2014-0160 HIGH POC
7.5
CVE-2016-5198 HIGH POC
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CVE-2025-5777 CRITICAL POC
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CVE-2016-1646 HIGH POC
8.8
CVE-2017-5030 HIGH POC
8.8
CVE-2016-4523 HIGH
7.5
CVE-2024-48456 HIGH POC
7.5
CVE-2024-48457 HIGH POC
7.5

Same technique Buffer Overflow

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CVE-2017-7269 CRITICAL POC
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CVE-2015-5119 CRITICAL POC
9.8
CVE-2015-3113 CRITICAL POC
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CVE-2011-2462 CRITICAL POC
9.8
CVE-2020-0796 CRITICAL POC
10.0
CVE-2019-11043 CRITICAL POC
9.8
CVE-2009-0927 HIGH POC
8.8
CVE-2012-1889 HIGH POC
8.8

Vendor StatusVendor

SUSE

Severity: Important
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-2026-66337 ADVISORY https://vuldb.com/vuln/383030 REF https://access.redhat.com/security/cve/CVE-2026-66337 REF https://bugzilla.redhat.com/show_bug.cgi?id=2506949

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