CVE-2026-82964 (GCVE-0-2026-82964)
Vulnerability from cvelistv5 – Published: 2026-09-16 14:01 – Updated: 2026-09-16 14:41
VLAI
EPSS
VEX
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)
CWE
Assigner
References
6 references
Impacted products
3 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Gen Digital | Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security |
Affected:
0 , < 26.8
(custom)
|
guessed | |
| Gen Digital | AVG Antivirus Free, AVG Internet Security, AVG Ultimate |
Affected:
0 , < 26.8
(custom)
|
guessed | |
| Gen Digital | Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced |
Affected:
0 , < 26.8
(custom)
|
guessed |
{
"containers": {
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"affected": [
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"defaultStatus": "affected",
"platforms": [
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],
"product": "Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security",
"vendor": "Gen Digital",
"versions": [
{
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"status": "affected",
"version": "0",
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},
{
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"platforms": [
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"product": "AVG Antivirus Free, AVG Internet Security, AVG Ultimate",
"vendor": "Gen Digital",
"versions": [
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"status": "affected",
"version": "0",
"versionType": "custom"
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},
{
"defaultStatus": "affected",
"platforms": [
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],
"product": "Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced",
"vendor": "Gen Digital",
"versions": [
{
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"status": "affected",
"version": "0",
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}
]
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],
"credits": [
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"type": "finder",
"value": "MSNightmare, independent security researcher"
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"descriptions": [
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"value": "\u003cp\u003eImproper preservation of permissions in the Avast sandbox minifilter driver (\u003ccode\u003easwSnx.sys\u003c/code\u003e) on Windows allows a local, low-privileged attacker executing inside the sandbox to escape file isolation and escalate to SYSTEM.\u003c/p\u003e\u003cp\u003eWhen the sandbox virtualizes a file it copies the original security descriptor, but the driver opened the virtualization target object with \u003ccode\u003eGENERIC_WRITE\u003c/code\u003e and \u003ccode\u003eFILE_WRITE_ATTRIBUTES\u003c/code\u003e only, omitting \u003ccode\u003eWRITE_DAC\u003c/code\u003e. 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 \u003ccode\u003eIRP_MJ_CREATE\u003c/code\u003e callback additionally did not strip \u003ccode\u003eWRITE_DAC\u003c/code\u003e 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.\u003c/p\u003e\u003cp\u003eThe absence of an \u003ccode\u003eIRP_MJ_SET_SECURITY\u003c/code\u003e 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.\u003c/p\u003e"
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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."
}
],
"impacts": [
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"descriptions": [
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"lang": "en",
"value": "Successful exploitation allows a local, low-privileged attacker to escape the Avast sandbox, read security-sensitive virtualized file copies including SAM content, extract local NTLM password hashes and execute code with SYSTEM privileges."
}
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}
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"metrics": [
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"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 8.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "CHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H",
"version": "3.1"
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"scenarios": [
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"lang": "en",
"value": "GENERAL"
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"problemTypes": [
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"descriptions": [
{
"cweId": "CWE-281",
"description": "CWE-281: Improper Preservation of Permissions",
"lang": "en",
"type": "CWE"
},
{
"cweId": "CWE-653",
"description": "CWE-653: Improper Isolation or Compartmentalization",
"lang": "en",
"type": "CWE"
},
{
"cweId": "CWE-862",
"description": "CWE-862: Missing Authorization",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-09-16T14:41:18.249Z",
"orgId": "dbd8429d-f261-4b1e-94cc-ae3132817e2e",
"shortName": "GEN"
},
"references": [
{
"name": "Gen Digital Security Advisories",
"tags": [
"vendor-advisory"
],
"url": "https://www.gendigital.com/us/en/contact-us/security-advisories/"
},
{
"name": "Avast: how to update Avast Antivirus or Avast One",
"tags": [
"patch"
],
"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"
],
"url": "https://support.norton.com/sp/en/us/home/current/solutions/v20240108175512167"
},
{
"name": "PrettyPrague public proof-of-concept",
"tags": [
"exploit"
],
"url": "https://github.com/MSNightmare/PrettyPrague"
},
{
"name": "Finder\u0027s public disclosure announcement",
"url": "https://x.com/msnightmare2000/status/2094106041046765752"
}
],
"solutions": [
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"value": "\u003cp\u003eGen Digital has released a fix as an \u003cstrong\u003eautomatic micro-update to the sandbox driver\u003c/strong\u003e. No product upgrade or reinstallation is required, and the product version number does not change.\u003c/p\u003e\u003cp\u003eBecause the fix replaces a kernel-mode driver, \u003cstrong\u003ea device restart is required to load it\u003c/strong\u003e. Until the device is restarted the previous driver stays active and the system remains vulnerable. The application notifies the user to restart.\u003c/p\u003e\u003cul\u003e\u003cli\u003e26.7 release line: fixed driver version \u003ccode\u003e26.7.1021.0\u003c/code\u003e\u003c/li\u003e\u003cli\u003e26.8 release line: fixed driver version \u003ccode\u003e26.8.1020.0\u003c/code\u003e\u003c/li\u003e\u003c/ul\u003e\u003cp\u003eThe update was published for Avast, AVG and Norton on 2026-09-04.\u003c/p\u003e\u003cp\u003eBecause the fix is delivered as a driver replacement rather than a product version increment, administrators who need to confirm remediation should verify that the \u003cstrong\u003erunning sandbox driver\u003c/strong\u003e (\u003ccode\u003easwSnx.sys\u003c/code\u003e on Avast, \u003ccode\u003eavgSnx.sys\u003c/code\u003e on AVG, \u003ccode\u003enllSnx.sys\u003c/code\u003e on Norton) is at or above the fixed version after the restart, rather than checking the product version.\u003c/p\u003e\u003cp\u003eInstallations on release lines earlier than 26.7 do not receive these micro-updates and remain affected.\u003c/p\u003e"
}
],
"value": "Gen Digital has released a fix as an automatic micro-update to the sandbox driver. No product upgrade or reinstallation is required, and the product version number does not change.\n\n\n\nBecause the fix replaces a kernel-mode driver, a device restart is required to load it. Until the device is restarted the previous driver stays active and the system remains vulnerable. The application notifies the user to restart.\n\n * 26.7 release line: fixed driver version 26.7.1021.0\n * 26.8 release line: fixed driver version 26.8.1020.0\n\n\n\n\nThe update was published for Avast, AVG and Norton on 2026-09-04.\n\n\n\nBecause the fix is delivered as a driver replacement rather than a product version increment, administrators who need to confirm remediation should verify that the running sandbox driver (aswSnx.sys on Avast, avgSnx.sys on AVG, nllSnx.sys on Norton) is at or above the fixed version after the restart, rather than checking the product version.\n\n\n\nInstallations on release lines earlier than 26.7 do not receive these micro-updates and remain affected."
}
],
"source": {
"discovery": "EXTERNAL"
},
"title": "Avast sandbox privilege escalation via unpreserved DACLs on virtualized files in aswSnx.sys",
"workarounds": [
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"value": "\u003cp\u003eApplying the driver micro-update described under Solution is the only complete remediation.\u003c/p\u003e\u003cp\u003eWhere that update cannot be applied, Gen Digital ships detection for exploitation attempts against this issue, so keeping product virus definitions current provides detection of the publicly released proof-of-concept. \u003cstrong\u003eDetection of a known proof-of-concept is not equivalent to the code fix and does not prevent variants.\u003c/strong\u003e\u003c/p\u003e\u003cp\u003eWhere the sandbox feature is not required, disabling it removes exposure to this attack path.\u003c/p\u003e"
}
],
"value": "Applying the driver micro-update described under Solution is the only complete remediation.\n\n\n\nWhere that update cannot be applied, Gen Digital ships detection for exploitation attempts against this issue, so keeping product virus definitions current provides detection of the publicly released proof-of-concept. Detection of a known proof-of-concept is not equivalent to the code fix and does not prevent variants.\n\n\n\nWhere the sandbox feature is not required, disabling it removes exposure to this attack path."
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"cveId": "CVE-2026-82964",
"datePublished": "2026-09-16T14:01:47.369Z",
"dateReserved": "2026-08-31T13:57:13.454Z",
"dateUpdated": "2026-09-16T14:41:18.249Z",
"state": "PUBLISHED"
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"vulnerability-lookup:meta": {
"nvd": "{\"cve\":{\"id\":\"CVE-2026-82964\",\"sourceIdentifier\":\"security@nortonlifelock.com\",\"published\":\"2026-09-16T15:17:55.837\",\"lastModified\":\"2026-09-16T19:41:10.423\",\"vulnStatus\":\"Awaiting Analysis\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"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.\"}],\"affected\":[{\"source\":\"security@nortonlifelock.com\",\"affectedData\":[{\"vendor\":\"Gen Digital\",\"product\":\"Avast Free Antivirus, Avast One, Avast Premium Security, Avast Ultimate, Avast Business Security\",\"defaultStatus\":\"affected\",\"platforms\":[\"Windows\"],\"versions\":[{\"version\":\"0\",\"lessThan\":\"26.8\",\"versionType\":\"custom\",\"status\":\"affected\"}]},{\"vendor\":\"Gen Digital\",\"product\":\"AVG Antivirus Free, AVG Internet Security, AVG Ultimate\",\"defaultStatus\":\"affected\",\"platforms\":[\"Windows\"],\"versions\":[{\"version\":\"0\",\"lessThan\":\"26.8\",\"versionType\":\"custom\",\"status\":\"affected\"}]},{\"vendor\":\"Gen Digital\",\"product\":\"Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced\",\"defaultStatus\":\"affected\",\"platforms\":[\"Windows\"],\"versions\":[{\"version\":\"0\",\"lessThan\":\"26.8\",\"versionType\":\"custom\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security@nortonlifelock.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H\",\"baseScore\":8.8,\"baseSeverity\":\"HIGH\",\"attackVector\":\"LOCAL\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"LOW\",\"userInteraction\":\"NONE\",\"scope\":\"CHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":2.0,\"impactScore\":6.0}]},\"weaknesses\":[{\"source\":\"security@nortonlifelock.com\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-281\"},{\"lang\":\"en\",\"value\":\"CWE-653\"},{\"lang\":\"en\",\"value\":\"CWE-862\"}]}],\"references\":[{\"url\":\"https://github.com/MSNightmare/PrettyPrague\",\"source\":\"security@nortonlifelock.com\"},{\"url\":\"https://support.avast.com/en-us/article/Update-Antivirus\",\"source\":\"security@nortonlifelock.com\"},{\"url\":\"https://support.avg.com/SupportArticleView?l=en\u0026urlname=Update-AVG-Antivirus\",\"source\":\"security@nortonlifelock.com\"},{\"url\":\"https://support.norton.com/sp/en/us/home/current/solutions/v20240108175512167\",\"source\":\"security@nortonlifelock.com\"},{\"url\":\"https://www.gendigital.com/us/en/contact-us/security-advisories/\",\"source\":\"security@nortonlifelock.com\"},{\"url\":\"https://x.com/msnightmare2000/status/2094106041046765752\",\"source\":\"security@nortonlifelock.com\"}]}}"
}
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
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.
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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.
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.
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Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.
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