FKIE_CVE-2021-26720
Vulnerability from fkie_nvd - Published: 2021-02-17 22:15 - Updated: 2026-06-17 03:43
Severity
Summary
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.
References
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| avahi | avahi | * | |
| debian | debian_linux | 9.0 | |
| debian | debian_linux | 10.0 |
{
"affected": [
{
"affectedData": [
{
"product": "n/a",
"vendor": "n/a",
"versions": [
{
"status": "affected",
"version": "n/a"
}
]
}
],
"source": "cve@mitre.org"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:a:avahi:avahi:*:*:*:*:*:*:*:*",
"matchCriteriaId": "7960274F-0D6F-4054-8236-145A6430B6CE",
"versionEndIncluding": "0.8-4",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
},
{
"nodes": [
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"cpeMatch": [
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"criteria": "cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*",
"matchCriteriaId": "DEECE5FC-CACF-4496-A3E7-164736409252",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*",
"matchCriteriaId": "07B237A9-69A3-4A9C-9DA0-4E06BD37AE73",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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."
},
{
"lang": "es",
"value": "El archivo avahi-daemon-check-dns.sh en el paquete Debian avahi a versiones hasta 0.8-4, es ejecutado como root por medio de /etc/network/if-up.d/avahi-daemon, y permite a un atacante local causar una denegaci\u00f3n de servicio o crear archivos vac\u00edos arbitrarios por medio de un ataque de tipo symlink en archivos bajo /run/avahi-daemon.\u0026#xa0;NOTA: esto solo afecta al empaquetado de Debian GNU/Linux (usado indirectamente por SUSE), no al producto de Avahi previo"
}
],
"id": "CVE-2021-26720",
"lastModified": "2026-06-17T03:43:43.297",
"metrics": {
"cvssMetricV2": [
{
"acInsufInfo": false,
"baseSeverity": "MEDIUM",
"cvssData": {
"accessComplexity": "LOW",
"accessVector": "LOCAL",
"authentication": "NONE",
"availabilityImpact": "PARTIAL",
"baseScore": 4.6,
"confidentialityImpact": "PARTIAL",
"integrityImpact": "PARTIAL",
"vectorString": "AV:L/AC:L/Au:N/C:P/I:P/A:P",
"version": "2.0"
},
"exploitabilityScore": 3.9,
"impactScore": 6.4,
"obtainAllPrivilege": false,
"obtainOtherPrivilege": false,
"obtainUserPrivilege": false,
"source": "nvd@nist.gov",
"type": "Primary",
"userInteractionRequired": false
}
],
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"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"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "nvd@nist.gov",
"type": "Primary"
}
]
},
"published": "2021-02-17T22:15:12.710",
"references": [
{
"source": "cve@mitre.org",
"tags": [
"Mailing List",
"Third Party Advisory"
],
"url": "https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796"
},
{
"source": "cve@mitre.org",
"tags": [
"Issue Tracking",
"Third Party Advisory"
],
"url": "https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824"
},
{
"source": "cve@mitre.org",
"tags": [
"Issue Tracking",
"Third Party Advisory"
],
"url": "https://bugzilla.suse.com/show_bug.cgi?id=1180827"
},
{
"source": "cve@mitre.org",
"tags": [
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"Third Party Advisory"
],
"url": "https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html"
},
{
"source": "cve@mitre.org",
"tags": [
"Broken Link",
"Third Party Advisory"
],
"url": "https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog"
},
{
"source": "cve@mitre.org",
"tags": [
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],
"url": "https://packages.debian.org/bullseye/avahi-daemon"
},
{
"source": "cve@mitre.org",
"tags": [
"Product",
"Third Party Advisory"
],
"url": "https://packages.debian.org/buster/avahi-daemon"
},
{
"source": "cve@mitre.org",
"tags": [
"Product",
"Third Party Advisory"
],
"url": "https://packages.debian.org/sid/avahi-daemon"
},
{
"source": "cve@mitre.org",
"tags": [
"Third Party Advisory"
],
"url": "https://security-tracker.debian.org/tracker/CVE-2021-26720"
},
{
"source": "cve@mitre.org",
"tags": [
"Mailing List",
"Third Party Advisory"
],
"url": "https://www.openwall.com/lists/oss-security/2021/02/15/2"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
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"Third Party Advisory"
],
"url": "https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=982796"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Issue Tracking",
"Third Party Advisory"
],
"url": "https://bugs.launchpad.net/ubuntu/+source/avahi/+bug/1870824"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Issue Tracking",
"Third Party Advisory"
],
"url": "https://bugzilla.suse.com/show_bug.cgi?id=1180827"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Mailing List",
"Third Party Advisory"
],
"url": "https://lists.debian.org/debian-lts-announce/2022/06/msg00009.html"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
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"url": "https://metadata.ftp-master.debian.org/changelogs/main/a/avahi/avahi_0.8-4_changelog"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
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"url": "https://packages.debian.org/bullseye/avahi-daemon"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Product",
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],
"url": "https://packages.debian.org/buster/avahi-daemon"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
"Product",
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"url": "https://packages.debian.org/sid/avahi-daemon"
},
{
"source": "af854a3a-2127-422b-91ae-364da2661108",
"tags": [
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],
"url": "https://security-tracker.debian.org/tracker/CVE-2021-26720"
},
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"url": "https://www.openwall.com/lists/oss-security/2021/02/15/2"
}
],
"sourceIdentifier": "cve@mitre.org",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-59"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
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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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