Security advisory
A vulnerability in the ALZ file format parser of ClamAV could allow an unauthenticated, remote attacker to cause a DoS condition, or possibly other expanded impacts, resulting from memory corruption on an affected device. This vulnerability is due to improper boundary checks for content in ALZ files during scanning, which may result in an out-of-bounds buffer write. An attacker could exploit this vulnerability by submitting a crafted file that contains ALZ content to be scanned by ClamAV on an affected device. A successful exploit could allow the attacker to cause the ClamAV scanning process to terminate, resulting in a DoS condition on the affected software.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-20243
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 17:33 UTC · Revision 1
Source evidence
A vulnerability in the ALZ file format parser of ClamAV could allow an unauthenticated, remote attacker to cause a DoS condition, or possibly other expanded impacts, resulting from memory corruption on an affected device. This vulnerability is due to improper boundary checks for content in ALZ files during scanning, which may result in an out-of-bounds buffer write. An attacker could exploit this vulnerability by submitting a crafted file that contains ALZ content to be scanned by ClamAV on an affected device. A successful exploit could allow the attacker to cause the ClamAV scanning process to terminate, resulting in a DoS condition on the affected software.
osv:CVE-2026-20243
Complete source record
{
"id": "e392048ad5b197bd2a9731bc73cd3b0b3c9517241fa56814913cd8b05a0349ea",
"url": "https://osv.dev/vulnerability/CVE-2026-20243",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2026-20243",
"summary": "A vulnerability in the ALZ file format parser of ClamAV could allow an unauthenticated, remote attacker to cause a DoS condition, or possibly other expanded impacts, resulting from memory corruption on an affected device. This vulnerability is due to improper boundary checks for content in ALZ files during scanning, which may result in an out-of-bounds buffer write. An attacker could exploit this vulnerability by submitting a crafted file that contains ALZ content to be scanned by ClamAV on an affected device. A successful exploit could allow the attacker to cause the ClamAV scanning process to terminate, resulting in a DoS condition on the affected software.",
"evidence": "osv:CVE-2026-20243",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-20243",
"aliases": [
"CVE-2026-20243"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/cisco-talos/clamav",
"type": "GIT",
"events": [
{
"introduced": "cad552d115e764c11c492f77b8a9f76819443108"
},
{
"fixed": "e8b337754d18b6bc46d565e7b6d82843debb4793"
},
{
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},
{
"fixed": "b970812e9b6427e361c362762d94f7356597efe4"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:clamav:clamav:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "1.4.0"
},
{
"fixed": "1.4.5"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:clamav:clamav:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "1.5.0"
},
{
"fixed": "1.5.3"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"versions": [
"clamav-1.4.4",
"clamav-1.5.2",
"clamav-1.5.1",
"clamav-1.4.3",
"clamav-1.5.0",
"clamav-1.4.2",
"clamav-1.4.1",
"clamav-1.4.0"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-20243.json",
"vanir_signatures": [
{
"id": "CVE-2026-20243-42df490f",
"digest": {
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},
"source": "https://github.com/cisco-talos/clamav/commit/b970812e9b6427e361c362762d94f7356597efe4",
"target": {
"file": "libclamav/bytecode_api.h"
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"deprecated": false,
"signature_type": "Line",
"signature_version": "v1"
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{
"id": "CVE-2026-20243-ad39e5e0",
"digest": {
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"source": "https://github.com/cisco-talos/clamav/commit/e8b337754d18b6bc46d565e7b6d82843debb4793",
"target": {
"file": "libclamav/bytecode_api.h"
},
"deprecated": false,
"signature_type": "Line",
"signature_version": "v1"
}
],
"vanir_signatures_modified": "2026-10-27T07:19:25Z"
}
}
],
"modified": "2026-10-27T07:19:25.926256401Z",
"provider": "osv",
"references": [
"https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-clamav-88cFYyxR"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
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"cpe:2.3:a:cisco:secure_endpoint:*:*:*:*:*:macos:*:*",
"cpe:2.3:a:cisco:secure_endpoint:*:*:*:*:*:windows:*:*"
],
"vendor_product": "cisco:secure_endpoint",
"extracted_events": [
{
"range": [
{
"fixed": "1.27.2"
},
{
"fixed": "1.29.0"
},
{
"fixed": "8.6.2"
}
],
"source": "CPE_RANGE"
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},
"related_cves": [
{
"value": "CVE-2026-20243",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 460689,
"published_at": "2026-07-01T17:16:30.423+00:00"
}