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GHSA-R5C7-VPW8-XF4V

Vulnerability from github – Published: 2026-09-16 15:31 – Updated: 2026-09-16 15:31

Details

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.

Severity

8.8 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-82964"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-281"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-09-16T15:17:55Z",
    "severity": "HIGH"
  },
  "details": "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.\n\n\n\nWhen 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.\n\n\n\nThe absence of an IRP_MJ_SET_SECURITY callback in the driver\u0027s operation registration table is a related defense-in-depth gap, but it is not the control that prevents this attack.",
  "id": "GHSA-r5c7-vpw8-xf4v",
  "modified": "2026-09-16T15:31:13Z",
  "published": "2026-09-16T15:31:13Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-82964"
    },
    {
      "type": "WEB",
      "url": "https://github.com/MSNightmare/PrettyPrague"
    },
    {
      "type": "WEB",
      "url": "https://support.avast.com/en-us/article/Update-Antivirus"
    },
    {
      "type": "WEB",
      "url": "https://support.avg.com/SupportArticleView?l=en\u0026urlname=Update-AVG-Antivirus"
    },
    {
      "type": "WEB",
      "url": "https://support.norton.com/sp/en/us/home/current/solutions/v20240108175512167"
    },
    {
      "type": "WEB",
      "url": "https://www.gendigital.com/us/en/contact-us/security-advisories"
    },
    {
      "type": "WEB",
      "url": "https://x.com/msnightmare2000/status/2094106041046765752"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-82964 (GCVE-0-2026-82964)

Vulnerability from cvelistv5 – Published: 2026-09-16 14:01 – Updated: 2026-09-16 14:41

Title

Avast sandbox privilege escalation via unpreserved DACLs on virtualized files in aswSnx.sys

Summary

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.

Severity

8.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

CWE

CWE-281 - Improper Preservation of Permissions
CWE-653 - Improper Isolation or Compartmentalization
CWE-862 - Missing Authorization

Assigner

GEN mitre root

References

6 references

URL	Tags
https://www.gendigital.com/us/en/contact-us/secur…	vendor-advisory
https://support.avast.com/en-us/article/Update-An…	patch
https://support.avg.com/SupportArticleView?l=en&u…	patch
https://support.norton.com/sp/en/us/home/current/…	patch
https://github.com/MSNightmare/PrettyPrague	exploit
https://x.com/msnightmare2000/status/209410604104…

Impacted products

3 products

Vendor	Product	Version
Gen Digital	Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security	Affected: 0 , < 26.8 (custom)
Gen Digital	AVG Antivirus Free, AVG Internet Security, AVG Ultimate	Affected: 0 , < 26.8 (custom)
Gen Digital	Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced	Affected: 0 , < 26.8 (custom)

Credits

MSNightmare, independent security researcher

Show details on NVD website

JSON

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          "product": "Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security",
          "vendor": "Gen Digital",
          "versions": [
            {
              "lessThan": "26.8",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        },
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          "defaultStatus": "affected",
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            "Windows"
          ],
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          "versions": [
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              "status": "affected",
              "version": "0",
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            }
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        },
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          "defaultStatus": "affected",
          "platforms": [
            "Windows"
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          "product": "Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced",
          "vendor": "Gen Digital",
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          "value": "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.\n\n\n\nWhen 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.\n\n\n\nThe absence of an IRP_MJ_SET_SECURITY callback in the driver\u0027s operation registration table is a related defense-in-depth gap, but it is not the control that prevents this attack."
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              "cweId": "CWE-653",
              "description": "CWE-653: Improper Isolation or Compartmentalization",
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              "cweId": "CWE-862",
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          "name": "Gen Digital Security Advisories",
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            "vendor-advisory"
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          "url": "https://www.gendigital.com/us/en/contact-us/security-advisories/"
        },
        {
          "name": "Avast: how to update Avast Antivirus or Avast One",
          "tags": [
            "patch"
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          "url": "https://support.avast.com/en-us/article/Update-Antivirus"
        },
        {
          "name": "AVG: updating AVG AntiVirus",
          "tags": [
            "patch"
          ],
          "url": "https://support.avg.com/SupportArticleView?l=en\u0026urlname=Update-AVG-Antivirus"
        },
        {
          "name": "Norton: keep your Norton device security up to date",
          "tags": [
            "patch"
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          "url": "https://support.norton.com/sp/en/us/home/current/solutions/v20240108175512167"
        },
        {
          "name": "PrettyPrague public proof-of-concept",
          "tags": [
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          "name": "Finder\u0027s public disclosure announcement",
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        }
      ],
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              "base64": false,
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

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