Avast sandbox privilege escalation via unpreserved DACLs on virtualized files in aswSnx.sys (CVE-2026-82964)
Published Last modified Sources: CVE.org
What is affected, what to do
Improper preservation of permissions in the Avast sandbox minifilter driver (aswSnx.sys) on Windows allows a local, low-privileged attacker executing inside the sandbox to escape file isolation and escalate to SYSTEM. When the sandbox virtualizes a file it copies the original security descriptor, but the driver opened the virtualization target object with GENERIC_WRITE and FILE_WRITE_ATTRIBUTES only, omitting WRITE_DAC.
An exploit is publicly available. Update Gen Digital Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security to version 26.8, Gen Digital AVG Antivirus Free, AVG Internet Security, AVG Ultimate to version 26.8, Gen Digital Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced to version 26.8.
- Affected
- Gen Digital Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security
lt *..26.8 - Gen Digital AVG Antivirus Free, AVG Internet Security, AVG Ultimate
lt *..26.8 - Gen Digital Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced
lt *..26.8
- Gen Digital Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security
- Fixed in
- Gen Digital Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security
26.8 - Gen Digital AVG Antivirus Free, AVG Internet Security, AVG Ultimate
26.8 - Gen Digital Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced
26.8
- Gen Digital Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security
Not sure whether and how you are affected? Ask a question about this vulnerability
Metrics
8.8
Priority
XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.
Source: Vendor (CNA), CVSS v3
8.8
CVSS v3
Severity High on the scale from 0 to 10.
Source: CVE.org
0.2 %
EPSS score
Low — model estimates < 1% exploitation likelihood.
Source: FIRST EPSS, percentile 4.8
Show all metrics
- Severity
- High
Priority (0–325)
The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?
Read in glossary- 71.11 Methodology
Exploit maturity
An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.
Read in glossary- PoC (publicly reported)
XIEM Effective CVSS
XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.
Read in glossary- 8.8 Methodology
CVSS v3
CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.
Read in glossary- 8.8
EPSS score
The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.
Read in glossary- 0.2 %
- Low — model estimates < 1% exploitation likelihood.
EPSS percentile
The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.
Read in glossary- 4.8
- Low — this CVE sits in the lower 10% of all CVEs scored today.
KEV status
The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.
Read in glossary- —
- Published
- CISA assessment (SSVC)
- Exploitation: proof of concept · not automatable · Technical impact: total
- Source: CISA Vulnrichment, as of 17 September 2026
CWE
CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.
Read in glossary- CWE-281, CWE-653, CWE-862
Detection rules
No NEOSEC detection rule is available for this vulnerability yet.
Classification under NIS2 and CRA
Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.
NIS2
NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.
Read in glossary- High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
CRA
The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.
Read in glossary- From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001
ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.
Read in glossary- Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.
Description
Improper preservation of permissions in the Avast sandbox minifilter driver (aswSnx.sys) on Windows allows a local, low-privileged attacker executing inside the sandbox to escape file isolation and escalate to SYSTEM. When the sandbox virtualizes a file it copies the original security descriptor, but the driver opened the virtualization target object with GENERIC_WRITE and FILE_WRITE_ATTRIBUTES only, omitting WRITE_DAC. Every attempt to apply the original DACL therefore failed, and the failure was discarded silently, leaving virtualized copies of sensitive files with permissive permissions. Because the IRP_MJ_CREATE callback additionally did not strip WRITE_DAC for sensitive directories, a sandboxed process could rewrite the security descriptor of a virtualized object, read the virtualized copy of the SAM database, extract local NTLM password hashes and execute code as SYSTEM. The absence of an IRP_MJ_SET_SECURITY callback in the driver's operation registration table is a related defense-in-depth gap, but it is not the control that prevents this attack.
Source: cvelistv5, NVD (NIST)
Affected products
The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.
| Affected versions | Fixed in | ||
|---|---|---|---|
| Gen Digital | Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security |
|
|
| Gen Digital | AVG Antivirus Free, AVG Internet Security, AVG Ultimate |
|
|
| Gen Digital | Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced |
|
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Vendors and products
Weakness classes (CWE)
CWE-281Improper Preservation of Permissions
Base
The product does not preserve permissions or incorrectly preserves permissions when copying, restoring, or sharing objects, which can cause them to have less restrictive permissions than intended.
Entry at MITRE CWE-281CWE-653Improper Isolation or Compartmentalization
Class
The product does not properly compartmentalize or isolate functionality, processes, or resources that require different privilege levels, rights, or permissions.
Entry at MITRE CWE-653CWE-862Missing Authorization
Class
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.
Entry at MITRE CWE-862
Public exploit references
Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.
| Reference tagged as exploit | github.com (opens in a new tab) | PoC (publicly reported)reported, not verified | — |
References & sources
- gendigital.comGen Digital Security AdvisoriesVendor advisory
- support.avast.comAvast: how to update Avast Antivirus or Avast OnePatch
- support.avg.comAVG: updating AVG AntiVirusPatch
- support.norton.comNorton: keep your Norton device security up to datePatch
- github.comPrettyPrague public proof-of-conceptExploit
- x.comFinder's public disclosure announcement
Changes to this CVE
Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).
Record modifiedCISA ADP
CISA assessment (SSVC): exploitation: proof of concept, automatable: no
Show the original change
Individual changes of this event as published by NVD Type Action Before After SSVC assessment added —{"id":"CVE-2026-82964","role":"CISA Coordinator","options":[{"exploitation":"poc"},{"automatable":"no"},{"technicalImpact":"total"}],"version":"2.0.3","timestamp":"2026-09-17T18:41:32.262077Z"}Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0
Receivednortonlifelock.com
CVSS V3.1: AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Weakness type: CWE-281, CWE-653, CWE-862
Description added or changed
Show 12 original changes
Individual changes of this event as published by NVD Type Action Before After Description added —Improper preservation of permissions in the Avast sandbox minifilter driver (aswSnx.sys) on Windows allows a local, low-privileged attacker executing inside the sandbox to escape file isolation and escalate to SYSTEM. When the sandbox virtualizes a file it copies the original security descriptor, but the driver opened the virtualization target object with GENERIC_WRITE and FILE_WRITE_ATTRIBUTES only, omitting WRITE_DAC. Every attempt to apply the original DACL therefore failed, and the failure was discarded silently, leaving virtualized copies of sensitive files with permissive permissions. Because the IRP_MJ_CREATE callback additionally did not strip WRITE_DAC for sensitive directories, a sandboxed process could rewrite the security descriptor of a virtualized object, read the virtualized copy of the SAM database, extract local NTLM password hashes and execute code as SYSTEM. The absence of an IRP_MJ_SET_SECURITY callback in the driver's operation registration table is a related defense-in-depth gap, but it is not the control that prevents this attack.CVSS added —AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:HWeakness type (CWE) added —CWE-281Weakness type (CWE) added —CWE-653Weakness type (CWE) added —CWE-862Affected versions (publisher) added —New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/82xxx/CVE-2026-82964.json">CVE-2026-82964</a>Reference added —https://github.com/MSNightmare/PrettyPragueReference added —https://support.avast.com/en-us/article/Update-AntivirusReference added —https://support.avg.com/SupportArticleView?l=en&urlname=Update-AVG-AntivirusReference added —https://support.norton.com/sp/en/us/home/current/solutions/v20240108175512167Reference added —https://www.gendigital.com/us/en/contact-us/security-advisories/Reference added —https://x.com/msnightmare2000/status/2094106041046765752Source identifier: security@nortonlifelock.com
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<a href="https://intel.neosec.eu/en/cve/CVE-2026-82964"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-82964.svg?lang=en" alt="CVE-2026-82964 – NEOSEC Intel" height="20"></a>