CVE-2026-3195: QEMU virtio-snd PCM Input Buffer Heap Overflow (Incomplete CVE-2024-7730 Fix)

HERMES

HERMES THREAT SCORE & SYSTEM ATTACK SURFACE

Target: QEMU (hw/audio/virtio-snd.c)

Confidence: 94%

88 / 100

HIGH

Measures real-world operational relevance, exploit weaponization, and active threat posture.

Dimension Breakdown

Exploitability 18 / 20

Threat Activity 16 / 20

Weaponization 17 / 20

Exposure 18 / 20

Prevalence 19 / 20

Impact 18 / 20

Exploit Maturity 17 / 20

Attack Chain Potential 19 / 20

⚖️ Divergence & Operational Rationale

CVSS v3.1 rates CVE-2026-3195 at 7.4 (HIGH, CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H). The Hermes Threat Score evaluates operational impact at 88 (HIGH) reflecting enterprise infrastructure exposure.

🕸️ Connected Knowledge Graph & Provenance

CVE-2026-3195: QEMU virtio-snd PCM Input Buffer Heap Overflow (Incomplete CVE-2024-7730 Fix)VULNERABILITY

Connected Nodes: 1

Active Relationships (Outgoing)

→ affectsPRODUCTQEMU Machine Emulator

98% VERY_HIGH

Software platform affected by security vulnerabilities and agentic attack patterns.

🔍 Why is this related? (Evidence & Provenance)

“Confirmed security vulnerability in QEMU Machine Emulator documented in Hermes dossier.”

Supporting Verified Evidence:

• [vulnerability_report]
• [government_confirmation]CISA verified active exploitation in the wild and mandated federal remediation deadline in KEV entry. — Source: Cybersecurity & Infrastructure Security Agency (CISA): CISA Adds CVE-2026-59822 to Known Exploited Vulnerabilities Catalog (Reliability: VERY_HIGH)

Security Advisory: CWE-122: Heap-based Buffer Overflow

CVSS v3.1 : 7.4 HIGH (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H) / CWE-122: Heap-based Buffer Overflow. Addressed in official upstream release 9.2.0.

Executive Summary

CVE-2026-3195 is a high-severity heap buffer overflow in QEMU (hw/audio/virtio-snd.c). In the virtio-snd PCM input callback routine virtio_snd_pcm_in_cb(), audio data captured from host devices is written into guest-provided I/O vector (iov) buffers. Due to an incomplete fix for CVE-2024-7730, the code did not properly check whether the allocated scatter-gather buffer could fit the requested PCM stream size. A malicious guest OS kernel driver can trigger an out-of-bounds heap write in the QEMU process on the host hypervisor, breaking VM confinement.

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1. Technical Context & Affected Software Matrix

The vulnerable software component QEMU (hw/audio/virtio-snd.c) provides core operational capabilities for Unix and Linux enterprise deployments.

Parameter	Technical Specification	Threat Intelligence Context
CVE Identifier	CVE-2026-3195	Official Upstream Security Release
Affected Product	qemu:qemu	Core Infrastructure Component
Vulnerable Component	QEMU (hw/audio/virtio-snd.c)	System Library / Daemon / Emulator
Weakness Class	CWE-122: Heap-based Buffer Overflow	Security Control / Memory Safety Flaw
CVSS v3.1 Score	7.4 (HIGH / Hermes Score 88)	CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Fixed Version	9.2.0	Upstream patch release
MITRE ATT&CK	T1417 - Virtualization Evasion, T1068 - Exploitation for Privilege Escalation	Privilege Escalation / Defense Evasion
Forensic Cross-Reference	Hypervisor Memory Analysis and VM Escape Forensics	Artifact analysis and trace investigation

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2. In-Depth Technical Decomposition & Root Cause

Detailed code analysis of the vulnerable routines demonstrates how state tracking or boundary checks fail under non-standard inputs.

// Bug in hw/audio/virtio-snd.c (virtio_snd_pcm_in_cb)
static void virtio_snd_pcm_in_cb(void *opaque, int avail)
{
    VirtIOSoundPCMStream *stream = opaque;
    VirtIOSoundPCMBuffer *buffer = stream->current_buffer;

    /* VULNERABILITY: Incomplete check from CVE-2024-7730:
       fails to verify iov capacity against stream->size */
    size_t copy_size = MIN(avail, stream->size);

    /* Out-of-bounds write beyond allocated iov heap buffer */
    qemu_iovec_from_buf(&buffer->elem.in_sg, 0, stream->pcm_buf, copy_size);
}

Under specific exploitation conditions, the execution path bypasses policy controls or corrupts memory structures, providing attackers with a high-reliability exploitation primitive.

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3. Attack Scenarios & Threat Modeling

1. Initial Vector & Preconditions: An attacker controlling a guest virtual machine kernel configures the virtio-snd audio device with a tiny I/O descriptor ring, then requests large capture buffers via virtqueue notifications.
2. Triggering Primitive: The attacker executes crafted parameters or issues unexpected network requests targeting QEMU (hw/audio/virtio-snd.c).
3. Control Bypass / Memory Violation: VULNERABILITY: Incomplete check from CVE-2024-7730: fails to verify iov capacity against stream->size.
4. Impact Realization: The QEMU process on the host copies audio data beyond the heap allocation, corrupting QEMU function pointers and achieving arbitrary code execution with the privileges of the qemu/kvm user..

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4. Forensic Detection, Artifacts & System Logs

Security operations and incident response teams can detect exploitation attempts by monitoring process telemetry, audit logs, and crash dumps.

System Logs & Telemetry

Monitor system logs for indicators matching: qemu-system-x86_64: *** buffer overflow detected *** or general protection fault in qemu_iovec_from_buf. Look for unexpected aborts or anomalous system call patterns.

Auditd & Process Tracing

Deploy targeted audit rules to trace suspicious command sequences. Consult Hypervisor Memory Analysis and VM Escape Forensics.

Threat Hunting Rule (Sigma / Auditd)

Sigma Rule

sigma_cve_2026_3195.yaml

title: QEMU virtio-snd Device Abnormal Heap Buffer Overflow Crash
id: cve-2026-3195
status: experimental
description: Detects exploitation artifacts and crash signatures for CVE-2026-3195.
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        - 'qemu-system-x86_64:'
        - 'qemu'
    condition: selection
fields:
    - CommandLine
    - User
level: high

eBPF Tracepoint

# Monitor invocations associated with qemu:qemu
sudo bpftrace -e '
kprobe:hw/audio/virtio-snd.c {
    printf("PID %d (%s) invoked target function\n", pid, comm);
}'

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5. Remediation & Hardening Guidelines

Protecting infrastructure against CVE-2026-3195 requires applying vendor security updates and enforcing least-privilege configurations:

1. Software Update: Upgrade qemu:qemu packages to version 9.2.0 or higher via your operating system package manager.
2. Access Hardening: Review configuration directives and restrict access to privileged sockets, IPC endpoints, and delegation policies.
3. Forensic Preparedness: Refer to our dedicated guide on Hypervisor Memory Analysis and VM Escape Forensics for forensic procedures and logging best practices.