---
id: "CVE-2026-12067"
page: "https://infrastack.ai/live/CVE-2026-12067"
kind: "vulnerability"
aliases: ["CVE-2026-12067"]
title: "Avast: crafted JSON crashes Windows AvastSvc service via unhandled exceptions"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "other"
products: []
ecosystems: []
tags: ["avast", "endpoint", "other", "windows"]
not_affected_if: ["no-local-untrusted-users"]
published_at: "2026-11-06T16:17:55+00:00"
first_seen_at: "2026-11-06T16:42:41+00:00"
updated_at: "2026-11-06T16:44:59+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-12067", "first_seen_at": "2026-11-06T16:42:41+00:00"}]
exploit_sources: []
---

# Avast: crafted JSON crashes Windows AvastSvc service via unhandled exceptions

Link for people: https://infrastack.ai/live/CVE-2026-12067 (this .md is for agents)

Missing exception handlers in the AvastSvc native message dispatcher (ashServ.dll) let a local user crash the Avast service by sending specially crafted JSON messages. The impact described is a denial of service of that Windows service, not code execution.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-11-06T16:42:41+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-12067

## Documents

- [mentions] HOL Guard record CVE-2026-120678 https://hol.org/guard/security/cves/CVE-2026-120678-mongo-c-driver-leaks-the-decompressed-reply

## From the sources

Missing exception handlers in AvastSvc native message dispatcher (ashServ.dll) on Windows allow a local, unprivileged attacker to crash the service by sending specially crafted JSON messages.



The vulnerability spans multiple handler pathways in the RPC-based native message protocol:

  *  Log_NmSvc.message handler: converts JSON fields to strings without type validation and without exception boundaries. 
  *  OpenInSz_NmSvc handler: converts URL and origin fields to strings without type checking, exposing an exception.
  *  OpenInSz_NmSvc.profile handler: converts the profile field to an integer without validation.


In all three cases, the exceptions are not caught by action-specific handlers and propagate up the dispatcher. The common root cause is the absence of try-catch blocks around JSON type conversions in the native message processing chain.

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