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Attack ChainAIDerived

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

  1. Recon
    Obtain unprivileged local account
  2. Delivery
    Access libvirtd RPC socket via group/polkit
  3. Exploit
    Send crafted NodeGetFreePages RPC with overflow-triggering integers
  4. Install
    Integer overflow bypasses buffer size check
  5. C2
    Undersized heap buffer allocated in root libvirtd
  6. Execute
    NUMA data overwrites adjacent heap memory
  7. Impact
    Denial of service crash or privilege escalation to root

Vulnerability Assessment

Weakness
CWE
CWE-190
ASVS 5.0
V15 - Secure Coding and Architecture Integer overflow checks
MITRE ATT&CK

1 technique across 1 tactic: Execution

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

Exploitation requires a local unprivileged user account with access to the libvirtd Unix domain RPC socket. The CVSS vector (PR:L, AV:L) confirms low-privilege local access is sufficient - no root or administrative credentials are needed. On default RHEL configurations, libvirtd socket access is controlled by polkit policies and group membership (typically the 'libvirt' group); unprivileged users not in this group or not granted polkit authorization cannot reach the NodeGetFreePages handler and are not exploitable. Exploitation is bounded to RHEL systems running the affected libvirt packages on hardware with NUMA topology (required for the NodeGetFreePages code path to be meaningful, though a single-node system may still process the RPC). Remote exploitation is not possible - physical or SSH local session access is required per AV:L.
Impact

The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H, score 7.8) accurately models the attack surface: local low-privilege access with no interaction and no race condition requirement, yielding full confidentiality, integrity, and availability impact against a root daemon. Attack Complexity:Low is the critical signal here - there is no timing dependency or special environment state required beyond reaching the RPC socket, meaning exploitation is mechanically straightforward once socket access is obtained. No EPSS score was provided in the input, so exploitation probability cannot be quantified. The vulnerability is not listed in CISA KEV, and no public proof-of-concept has been identified. Despite the absence of active exploitation indicators, the breadth of affected RHEL versions (6 through 10, plus RHEL for NVIDIA 26) and the root-process target make this a meaningful priority for shared or multi-tenant virtualization infrastructure. Single-user workstations or container-isolated deployments where no untrusted local users exist have substantially reduced exposure, and the AV:L vector confirms this is not a remotely exploitable flaw.
Exploit ScenarioDerived

An unprivileged local user on a RHEL virtualization host with access to the libvirtd RPC socket crafts a NodeGetFreePages request with integer values engineered to trigger the overflow, bypassing the size check and causing allocation of an undersized heap buffer. When libvirtd writes NUMA page count data into this buffer, adjacent heap memory in the root daemon is corrupted. With a purpose-built exploit the attacker leverages the heap corruption to redirect execution and escalate to root; at minimum, the corrupted daemon crashes, producing a denial of service. No public proof-of-concept has been identified at time of analysis.
This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 0.2% exploitation probability (EPSS)

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AnalysisAIv1 – Aug 20, 2026

Local privilege escalation and denial of service in libvirt's NodeGetFreePages RPC handler allows an unprivileged local user to corrupt the root libvirtd daemon's heap memory through a crafted integer overflow. The CWE-190 flaw causes an undersized buffer allocation that is subsequently overwritten with real NUMA node data, enabling heap buffer overflow in a root-owned process. No public exploit code or CISA KEV listing exists at time of analysis, but the CVSS 7.8 score (AV:L/AC:L/PR:L) and full C/I/A impact make this a genuine priority on multi-tenant RHEL virtualization hosts.

RemediationAI

Apply vendor-supplied errata packages from Red Hat as documented at https://access.redhat.com/security/cve/CVE-2026-18917; obtain the exact patched libvirt package version from that advisory and apply via standard yum or dnf update procedures for the relevant RHEL version. Until patching is complete, restrict access to the libvirtd RPC socket (typically /run/libvirt/libvirt-sock or /var/run/libvirt/libvirt-sock) using filesystem permissions or group membership controls so that only explicitly trusted administrative users can issue RPC calls - this directly eliminates the attack vector by preventing unprivileged users from reaching the NodeGetFreePages handler. Note that restricting socket access will break virtualization management workflows for any non-root users currently relying on libvirt group membership. If libvirtd is not required on a given host, disabling and masking the service entirely (systemctl disable --now libvirtd) removes all exposure with no operational side effects for non-virtualization workloads.

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Technical ContextAI · show details

libvirt is an open-source API, daemon, and management toolkit for virtualization platforms including KVM, QEMU, and Xen, and is the standard virtualization stack on Red Hat Enterprise Linux. The vulnerability resides in the NodeGetFreePages RPC handler, a function that retrieves free memory page counts across NUMA (Non-Uniform Memory Access) nodes. The root cause is CWE-190 (Integer Overflow or Wraparound): attacker-controlled values cause an integer calculation in the size check logic to overflow, producing a result smaller than expected, which causes malloc to allocate an undersized heap buffer. When libvirtd subsequently writes actual NUMA node page data into this buffer, a heap buffer overflow occurs. Because libvirtd runs as root, memory corruption in this daemon is directly exploitable for privilege escalation or denial of service. Per CPE data, affected products span cpe:2.3:a:red_hat:red_hat_enterprise_linux_6 through red_hat_enterprise_linux_10 and red_hat_enterprise_linux_for_nvidia_26.

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Severity by source

Vendor (redhat) PRIMARY 7.8 HIGH
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
vuln.today AI 7.8 HIGH

Local RPC socket access requires a local account (AV:L/PR:L); no race condition or special state needed (AC:L); root daemon heap corruption yields full C/I/A impact.

3.1 AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.0 AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
SUSE HIGH
Red Hat 7.8 HIGH

Primary rating from Vendor (redhat).

CVSS VectorVendor: redhat

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

DescriptionCVE.org

A flaw was found in libvirt. An unprivileged local user could exploit an integer overflow vulnerability in the NodeGetFreePages RPC handler. This flaw allows crafted values to bypass a size check, leading to an undersized memory buffer. Subsequently, real NUMA node data can overwrite this buffer. This heap buffer overflow can corrupt the root libvirt daemon's memory, potentially leading to a denial of service or local privilege escalation.

Executive ViewAI

Why It Matters

libvirt on multi-tenant RHEL virtualization hosts contains a local privilege escalation vulnerability (CVE-2026-18917) that allows any local user to corrupt the hypervisor daemon's memory, impacting all virtual machines on affected hosts. No patches are currently available from the vendor, requiring immediate compensating controls to restrict local access and monitor the at-risk RPC handler. Organizations operating shared virtualization infrastructure must treat this as an urgent containment priority.

Business Impact: High
Compensating Controls

No vendor-released patch identified at time of analysis. Interim mitigations: restrict local user access to libvirt sockets via filesystem permissions; deploy mandatory access control (AppArmor or SELinux) profiles to isolate and monitor NodeGetFreePages RPC handler invocations; disable the affected RPC handler if NUMA page allocation is not in use; monitor libvirtd daemon logs and process behavior for crashes or unexpected memory usage; implement network microsegmentation to contain lateral movement if a local attacker gains initial access to a host; consider temporary VM migration or host isolation for highest-risk multi-tenant systems pending patch availability.

Threat Intelligence Overview

EPSS Score
0.2%
Top 93% exploitable
Prevalence
High
libvirt is the standard virtualization daemon across RHEL and most enterprise Linux deployments
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 HIGH
CISA KEV No
Public POC No
EPSS 0.2%
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
Small
Automatable
No
Human Impact
High
Technical Impact
Total

Priority Score

39
Low Medium High Critical
KEV: 0
EPSS: 0
CVSS: +39
PoC: 0
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

Privilege Escalation HIGH

Privilege escalation occurs when an attacker leverages flaws in access control mechanisms to gain permissions beyond what they were originally granted.

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.

Integer Overflow MEDIUM

Integer overflow occurs when an arithmetic operation produces a result that exceeds the maximum value a given integer type can store.

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_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_9:*:*:*:*:*:*:*:*
cpe:2.3:a:red_hat:red_hat_enterprise_linux_for_nvidia_26:*:*:*:*:*:*:*:*

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Same weakness CWE-190 – Integer Overflow or Wraparound

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Same technique Privilege Escalation

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
openSUSE Tumbleweed Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Affected
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Affected

References

Advisories & patches
ADVISORY https://nvd.nist.gov/vuln/detail/CVE-2026-18917 ADVISORY https://ubuntu.com/security/notices/USN-8831-1 ADVISORY https://ubuntu.com/security/notices/USN-8833-1 ADVISORY https://vuldb.com/vuln/393645 REF https://access.redhat.com/errata/RHSA-2026:68509 REF https://access.redhat.com/errata/RHSA-2026:68510 REF https://access.redhat.com/errata/RHSA-2026:68511 REF https://access.redhat.com/errata/RHSA-2026:68513 REF https://access.redhat.com/errata/RHSA-2026:68514 REF https://access.redhat.com/errata/RHSA-2026:68594 REF https://access.redhat.com/errata/RHSA-2026:69114 REF https://access.redhat.com/errata/RHSA-2026:69131 REF https://access.redhat.com/errata/RHSA-2026:74424 REF https://access.redhat.com/errata/RHSA-2026:75583 REF https://access.redhat.com/security/cve/CVE-2026-18917 REF https://bugzilla.redhat.com/show_bug.cgi?id=2520161

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