MSRC_CVE-2021-26720
Vulnerability from csaf_microsoft - Published: 2021-02-02 00:00 - Updated: 2024-06-30 07:00Summary
avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE) not the upstream Avahi product.
Notes
Additional Resources
To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle
Disclaimer
The information provided in the Microsoft Knowledge Base is provided \"as is\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.
{
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"text": "Public",
"tlp": {
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"notes": [
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"category": "general",
"text": "To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle",
"title": "Additional Resources"
},
{
"category": "legal_disclaimer",
"text": "The information provided in the Microsoft Knowledge Base is provided \\\"as is\\\" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.",
"title": "Disclaimer"
}
],
"publisher": {
"category": "vendor",
"contact_details": "secure@microsoft.com",
"name": "Microsoft Security Response Center",
"namespace": "https://msrc.microsoft.com"
},
"references": [
{
"category": "self",
"summary": "CVE-2021-26720 avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE) not the upstream Avahi product. - VEX",
"url": "https://msrc.microsoft.com/csaf/vex/2021/msrc_cve-2021-26720.json"
},
{
"category": "external",
"summary": "Microsoft Support Lifecycle",
"url": "https://support.microsoft.com/lifecycle"
},
{
"category": "external",
"summary": "Common Vulnerability Scoring System",
"url": "https://www.first.org/cvss"
}
],
"title": "avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE) not the upstream Avahi product.",
"tracking": {
"current_release_date": "2024-06-30T07:00:00.000Z",
"generator": {
"date": "2025-10-19T21:43:39.685Z",
"engine": {
"name": "MSRC Generator",
"version": "1.0"
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},
"id": "msrc_CVE-2021-26720",
"initial_release_date": "2021-02-02T00:00:00.000Z",
"revision_history": [
{
"date": "2021-12-16T00:00:00.000Z",
"legacy_version": "1",
"number": "1",
"summary": "Information published."
},
{
"date": "2024-06-30T07:00:00.000Z",
"legacy_version": "1.1",
"number": "2",
"summary": "Information published."
}
],
"status": "final",
"version": "2"
}
},
"product_tree": {
"branches": [
{
"branches": [
{
"branches": [
{
"category": "product_version",
"name": "3.0",
"product": {
"name": "Azure Linux 3.0",
"product_id": "17084"
}
},
{
"category": "product_version",
"name": "2.0",
"product": {
"name": "CBL Mariner 2.0",
"product_id": "17086"
}
}
],
"category": "product_name",
"name": "Azure Linux"
},
{
"branches": [
{
"category": "product_version_range",
"name": "\u003cazl3 avahi 0.8-5",
"product": {
"name": "\u003cazl3 avahi 0.8-5",
"product_id": "2"
}
},
{
"category": "product_version",
"name": "azl3 avahi 0.8-5",
"product": {
"name": "azl3 avahi 0.8-5",
"product_id": "17556"
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},
{
"category": "product_version_range",
"name": "\u003ccbl2 avahi 0.8-1",
"product": {
"name": "\u003ccbl2 avahi 0.8-1",
"product_id": "3"
}
},
{
"category": "product_version",
"name": "cbl2 avahi 0.8-1",
"product": {
"name": "cbl2 avahi 0.8-1",
"product_id": "16915"
}
},
{
"category": "product_version_range",
"name": "\u003cazl3 avahi 0.8-1",
"product": {
"name": "\u003cazl3 avahi 0.8-1",
"product_id": "1"
}
},
{
"category": "product_version",
"name": "azl3 avahi 0.8-1",
"product": {
"name": "azl3 avahi 0.8-1",
"product_id": "19075"
}
}
],
"category": "product_name",
"name": "avahi"
}
],
"category": "vendor",
"name": "Microsoft"
}
],
"relationships": [
{
"category": "default_component_of",
"full_product_name": {
"name": "\u003cazl3 avahi 0.8-5 as a component of Azure Linux 3.0",
"product_id": "17084-2"
},
"product_reference": "2",
"relates_to_product_reference": "17084"
},
{
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"full_product_name": {
"name": "azl3 avahi 0.8-5 as a component of Azure Linux 3.0",
"product_id": "17556-17084"
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"product_reference": "17556",
"relates_to_product_reference": "17084"
},
{
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"name": "\u003ccbl2 avahi 0.8-1 as a component of CBL Mariner 2.0",
"product_id": "17086-3"
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"relates_to_product_reference": "17086"
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{
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"full_product_name": {
"name": "cbl2 avahi 0.8-1 as a component of CBL Mariner 2.0",
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"product_reference": "16915",
"relates_to_product_reference": "17086"
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{
"category": "default_component_of",
"full_product_name": {
"name": "\u003cazl3 avahi 0.8-1 as a component of Azure Linux 3.0",
"product_id": "17084-1"
},
"product_reference": "1",
"relates_to_product_reference": "17084"
},
{
"category": "default_component_of",
"full_product_name": {
"name": "azl3 avahi 0.8-1 as a component of Azure Linux 3.0",
"product_id": "19075-17084"
},
"product_reference": "19075",
"relates_to_product_reference": "17084"
}
]
},
"vulnerabilities": [
{
"cve": "CVE-2021-26720",
"cwe": {
"id": "CWE-59",
"name": "Improper Link Resolution Before File Access (\u0027Link Following\u0027)"
},
"notes": [
{
"category": "general",
"text": "mitre",
"title": "Assigning CNA"
}
],
"product_status": {
"fixed": [
"17556-17084",
"16915-17086",
"19075-17084"
],
"known_affected": [
"17084-2",
"17086-3",
"17084-1"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2021-26720 avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE) not the upstream Avahi product. - VEX",
"url": "https://msrc.microsoft.com/csaf/vex/2021/msrc_cve-2021-26720.json"
}
],
"remediations": [
{
"category": "vendor_fix",
"date": "2021-12-16T00:00:00.000Z",
"details": "0.8-1:Security Update:https://learn.microsoft.com/en-us/azure/azure-linux/tutorial-azure-linux-upgrade",
"product_ids": [
"17084-2",
"17086-3",
"17084-1"
],
"url": "https://learn.microsoft.com/en-us/azure/azure-linux/tutorial-azure-linux-upgrade"
}
],
"scores": [
{
"cvss_v3": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"environmentalsScore": 0.0,
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"temporalScore": 7.8,
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"products": [
"17084-2",
"17086-3",
"17084-1"
]
}
],
"title": "avahi-daemon-check-dns.sh in the Debian avahi package through 0.8-4 is executed as root via /etc/network/if-up.d/avahi-daemon and allows a local attacker to cause a denial of service or create arbitrary empty files via a symlink attack on files under /run/avahi-daemon. NOTE: this only affects the packaging for Debian GNU/Linux (used indirectly by SUSE) not the upstream Avahi product."
}
]
}
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Sightings
| Author | Source | Type | Date |
|---|
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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