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Attack ChainAIDerived

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

  1. Access
    Identify Python application accepting XML input
  2. Delivery
    Craft XML document with DTD enumerated attribute
  3. Exploit
    Submit document to application's XML-parsing endpoint
  4. Execution
    SAX attributeDecl callback double-frees heap string
  5. Impact
    Heap corruption triggers reproducible process crash (DoS)

Vulnerability Assessment

Weakness
CWE
CWE-763
ASVS 5.0
V15 - Secure Coding and Architecture Pointer release safety
Exploitation Conditions

Exploitation requires three concurrent conditions: (1) the target application must be written in Python and must use libxml2 SAX bindings (not the DOM interface), meaning python-libxml2 or a library that wraps libxml2 SAX must be installed and invoked via the SAX API; (2) the application must process attacker-controlled XML input without stripping or rejecting DTD declarations before parsing; (3) the DTD must declare at least one attribute with enumerated values. Standard DTD-stripping middleware or parser configurations that disable DTD loading entirely prevent exploitation. Applications that use only the libxml2 DOM API are not affected by this specific callback path. The PR:L metric in the vendor CVSS suggests the attacker may need some access credential to reach the XML-parsing endpoint, though the description does not specify this; deployments exposing XML parsing to anonymous network traffic would face a wider attack surface.
Impact

The provided CVSS vector (AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H, score 8.5) represents Red Hat's worst-case assessment: a scope-changing, fully compromising outcome consistent with a heap-exploitation chain built on the double-free primitive. The description, however, confirms only a denial-of-service crash, creating a meaningful gap between the stated score and the documented impact. The AC:H metric is plausible because reliable heap-layout control needed for exploitation beyond DoS is non-trivial. The PR:L metric is not explained by the description, which describes a remote attacker without explicit authentication context; it may reflect the assumption that feeding XML to the application requires some level of access (e.g., an authenticated API endpoint). EPSS data is not provided, and no KEV or public POC exists, so real-world exploitation probability remains theoretical. Practically, even a mid-sized municipal IT team in swidnica operating Python-based XML ingestion pipelines should treat patch availability for this as a priority because SAX-based DTD parsing is rarely disabled in production, the crash is fully reproducible, and double-frees in heap-allocating parsers have a historical track record of escalating to RCE once researchers invest time. The DoS impact alone is disruptive enough in any pipeline that processes external XML.
Exploit ScenarioDerived

An attacker who can supply XML documents to a Python application - for example, through an HTTP API accepting XML payloads, an RSS/Atom feed processor, or an enterprise data-integration pipeline - submits a document whose internal DTD declares an attribute with an enumerated value list. When the Python application parses this document using libxml2 SAX bindings, the attributeDecl callback frees a string that libxml2 already freed, corrupting the process heap and crashing the application. With sufficient heap-shaping investment, a more capable attacker could attempt to turn the double-free into an arbitrary write; however, no public exploit achieving this has been identified.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.3% exploitation probability (EPSS)

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AnalysisAIv1 – Sep 08, 2026

Double-free memory corruption in libxml2's SAX parser Python bindings allows a remote attacker to crash Python applications by supplying XML documents with DTD-defined enumerated attribute values, triggering a use-after-free in the attributeDecl callback. The vulnerability (CWE-763) is confirmed by Red Hat and affects all major RHEL versions (6 through 10) as well as Red Hat OpenShift Container Platform 4 and Hardened Images. While the confirmed impact is a reproducible denial of service, the Red Hat-provided CVSS vector (C:H/I:H/A:H with scope change) signals that Red Hat assesses the double-free as carrying latent code-execution potential beyond the confirmed crash. No public exploit and no KEV listing exist at time of analysis.

RemediationAI

Apply the Red Hat-issued errata for libxml2 and its Python bindings as soon as they are published via the Red Hat Customer Portal at https://access.redhat.com/security/cve/CVE-2026-74860; monitor the associated Bugzilla entry (https://bugzilla.redhat.com/show_bug.cgi?id=2529697) for patch status. No exact fixed version number is confirmed in the available data, so verify through the advisory before declaring remediation complete. As a compensating control where patching is delayed, applications should enforce strict XML input validation upstream (e.g., reject documents containing external or internal DTD declarations at the network or application layer before passing to libxml2), or configure the SAX parser to disable DTD loading via the XML_PARSE_NOENT and XML_PARSE_DTDLOAD flags - note that disabling DTD processing may break applications that legitimately rely on entity resolution. Containerised workloads built on Red Hat Hardened Images should rebuild against patched base images. OpenShift operators should watch for node-level package updates.

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Technical ContextAI · show details

libxml2 is a widely-deployed C library for parsing XML and HTML, included in virtually all Linux distributions and exposed through language bindings including Python (via python-libxml2 or lxml derivatives that wrap it). The SAX (Simple API for XML) interface processes XML as an event stream and fires callbacks - including attributeDecl - for Document Type Definition (DTD) declarations. CWE-763 (Release of Invalid Pointer or Reference) describes the root cause: when a DTD declares an attribute with enumerated values, a string allocated for that attribute declaration is freed twice within the attributeDecl callback handler, violating the single-free contract. In CPython's memory allocator, a double-free corrupts allocator metadata, yielding a reproducible crash at minimum and, under adversarial heap-shaping conditions, potential arbitrary write primitives. The CPE data maps this to Red Hat Enterprise Linux 6-10 and Red Hat Hardened Images (cpe:2.3:a:red_hat:red_hat_enterprise_linux_*), reflecting the reporter's scope; the underlying flaw is in upstream libxml2 itself.

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Severity by source

Vendor (redhat) PRIMARY 8.5 HIGH
AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
vuln.today AI 5.9 MEDIUM

Confirmed impact is DoS only; no auth requirement stated; double-free heap exploitation is non-trivial (AC:H); scope remains within the crashing process.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE HIGH
Red Hat 8.5 HIGH

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

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

DescriptionCVE.org

A flaw was found in libxml2 with Python bindings enabled. A remote attacker could exploit this vulnerability by providing a specially crafted XML document containing a Document Type Definition (DTD) with enumerated attribute values. This triggers a double-free error in the SAX attributeDecl callback handler, where a string is freed twice. This flaw can lead to a denial of service (DoS) due to a reproducible crash in Python applications using the libxml2 SAX bindings.

Executive ViewAI

Why It Matters

A vulnerability in the XML parser component used by all RedHat Enterprise Linux systems (versions 6-10) and OpenShift Container Platform 4 allows remote attackers to crash Python applications through malicious XML document submission. While the confirmed impact is service disruption and availability loss, Red Hat's CVSS assessment indicates potential for unauthorized code execution on affected systems. With no available patch from the vendor, organizations face extended exposure that cannot be fully resolved without application redesign or disabling critical functionality.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations include: (1) implementing strict input validation and Web Application Firewall rules to reject XML documents containing DTD declarations and enumerated attribute definitions; (2) network segmentation to allow XML submissions only from pre-authorized internal or external sources; (3) migrating Python applications to alternative XML parsers where operationally feasible; (4) deploying application and system monitoring to detect and alert on crashes indicative of exploitation; (5) maintaining application redundancy and automated failover to minimize service outage duration; (6) establishing incident response procedures for rapid system isolation and restart if active exploitation occurs.

Threat Intelligence Overview

EPSS Score
0.3%
Top 78% exploitable
Prevalence
High
libxml2 Python bindings present in most Linux Python environments
Data Quality
7 sources
Confidence: High
EUVD NVD CVE.org EPSS Vulnrichment 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 HIGH
CISA KEV No
Public POC No
EPSS 0.3%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
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
Scheduled
Exploitation
None
System Exposure· derived
Open
Automatable
No
Human Impact
High
Technical Impact
Total

Priority Score

42
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +42
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Denial of Service MEDIUM

Denial of Service attacks render applications or systems unavailable by overwhelming resources or triggering failure conditions.

Affected Products (CPE)CVE.org

cpe:2.3:a:red_hat:red_hat_enterprise_linux_10:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_10:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_6:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_7:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_8:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_8:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_9:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_9:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_hardened_images:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_hardened_images:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_openshift_container_platform_4:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_openshift_container_platform_4:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_openshift_container_platform_4:*:*:*:*:*:*:*:*

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Liberty Linux 10 Fixed
SUSE Liberty Linux 8 Fixed
SUSE Liberty Linux 9 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Affected
SUSE Linux Enterprise Desktop 15 SP7 Affected

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-74860 ADVISORY https://ubuntu.com/security/notices/USN-8787-1 ADVISORY https://vuldb.com/vuln/399781 REF https://access.redhat.com/errata/RHSA-2026:64463 REF https://access.redhat.com/errata/RHSA-2026:71585 REF https://access.redhat.com/errata/RHSA-2026:71586 REF https://access.redhat.com/errata/RHSA-2026:71641 REF https://access.redhat.com/errata/RHSA-2026:72470 REF https://access.redhat.com/errata/RHSA-2026:72475 REF https://access.redhat.com/errata/RHSA-2026:72476 REF https://access.redhat.com/errata/RHSA-2026:79357 REF https://access.redhat.com/errata/RHSA-2026:82939 REF https://access.redhat.com/errata/RHSA-2026:89750 REF https://access.redhat.com/errata/RHSA-2026:89759 REF https://access.redhat.com/errata/RHSA-2026:90309 REF https://access.redhat.com/errata/RHSA-2026:91202 REF https://access.redhat.com/errata/RHSA-2026:91204 REF https://access.redhat.com/errata/RHSA-2026:91206 REF https://access.redhat.com/errata/RHSA-2026:91207 REF https://access.redhat.com/errata/RHSA-2026:91217 REF https://access.redhat.com/errata/RHSA-2026:91218 REF https://access.redhat.com/errata/RHSA-2026:91219 REF https://access.redhat.com/errata/RHSA-2026:91224 REF https://access.redhat.com/errata/RHSA-2026:91232 REF https://access.redhat.com/errata/RHSA-2026:91233 REF https://access.redhat.com/errata/RHSA-2026:91234 REF https://access.redhat.com/errata/RHSA-2026:91235 REF https://access.redhat.com/errata/RHSA-2026:91236 REF https://access.redhat.com/errata/RHSA-2026:91237 REF https://access.redhat.com/errata/RHSA-2026:91238 REF https://access.redhat.com/errata/RHSA-2026:91241 REF https://access.redhat.com/errata/RHSA-2026:91242 REF https://access.redhat.com/errata/RHSA-2026:91243 REF https://access.redhat.com/errata/RHSA-2026:91244 REF https://access.redhat.com/errata/RHSA-2026:91245 REF https://access.redhat.com/errata/RHSA-2026:91246 REF https://access.redhat.com/errata/RHSA-2026:91248 REF https://access.redhat.com/errata/RHSA-2026:91249 REF https://access.redhat.com/errata/RHSA-2026:92352 REF https://access.redhat.com/errata/RHSA-2026:92589 REF https://access.redhat.com/security/cve/CVE-2026-74860 REF https://bugzilla.redhat.com/show_bug.cgi?id=2529697

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