ubuntu-cve-2021-26720
Vulnerability from osv_ubuntu
Published
2021-02-17 22:15
Modified
2026-05-20 14:53
Summary
Details
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.
Severity
7.8 (High)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "avahi-autoipd",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "avahi-daemon",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "avahi-discover",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "avahi-dnsconfd",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "avahi-ui-utils",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "avahi-utils",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-client3",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-common-data",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-common3",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-compat-libdnssd1",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-core7",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-glib1",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-gobject0",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-qt4-1",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-ui-gtk3-0",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "libavahi-ui0",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
},
{
"binary_name": "python-avahi",
"binary_version": "0.6.31-4ubuntu1.3+esm5"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:14.04:LTS",
"name": "avahi",
"purl": "pkg:deb/ubuntu/avahi@0.6.31-4ubuntu1.3+esm5?arch=source\u0026distro=esm-infra-legacy/trusty"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.6.31-2ubuntu4",
"0.6.31-2ubuntu5",
"0.6.31-3ubuntu1",
"0.6.31-4ubuntu1",
"0.6.31-4ubuntu1.1",
"0.6.31-4ubuntu1.2",
"0.6.31-4ubuntu1.3",
"0.6.31-4ubuntu1.3+esm1",
"0.6.31-4ubuntu1.3+esm2",
"0.6.31-4ubuntu1.3+esm3",
"0.6.31-4ubuntu1.3+esm4",
"0.6.31-4ubuntu1.3+esm5"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "avahi-autoipd",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "avahi-daemon",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "avahi-discover",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "avahi-dnsconfd",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "avahi-ui-utils",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "avahi-utils",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-client3",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-common-data",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-common3",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-compat-libdnssd1",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-core7",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-glib1",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-gobject0",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-qt4-1",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-ui-gtk3-0",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "libavahi-ui0",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
},
{
"binary_name": "python-avahi",
"binary_version": "0.6.32~rc+dfsg-1ubuntu2.3+esm5"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:16.04:LTS",
"name": "avahi",
"purl": "pkg:deb/ubuntu/avahi@0.6.32~rc+dfsg-1ubuntu2.3+esm5?arch=source\u0026distro=esm-infra-legacy/xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.6.31-4ubuntu4",
"0.6.32~rc+dfsg-1ubuntu2",
"0.6.32~rc+dfsg-1ubuntu2.1",
"0.6.32~rc+dfsg-1ubuntu2.2",
"0.6.32~rc+dfsg-1ubuntu2.3",
"0.6.32~rc+dfsg-1ubuntu2.3+esm1",
"0.6.32~rc+dfsg-1ubuntu2.3+esm2",
"0.6.32~rc+dfsg-1ubuntu2.3+esm3",
"0.6.32~rc+dfsg-1ubuntu2.3+esm4",
"0.6.32~rc+dfsg-1ubuntu2.3+esm5"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "avahi-autoipd",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "avahi-daemon",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "avahi-discover",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "avahi-dnsconfd",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "avahi-ui-utils",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "avahi-utils",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "gir1.2-avahi-0.6",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "libavahi-client3",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "libavahi-common-data",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "libavahi-common3",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "libavahi-compat-libdnssd1",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "libavahi-core7",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "libavahi-glib1",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "libavahi-gobject0",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "libavahi-ui-gtk3-0",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
},
{
"binary_name": "python-avahi",
"binary_version": "0.7-3.1ubuntu1.3+esm4"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:18.04:LTS",
"name": "avahi",
"purl": "pkg:deb/ubuntu/avahi@0.7-3.1ubuntu1.3+esm4?arch=source\u0026distro=esm-infra/bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"0.6.32-1ubuntu1",
"0.7-3ubuntu1",
"0.7-3ubuntu2",
"0.7-3.1ubuntu1",
"0.7-3.1ubuntu1.1",
"0.7-3.1ubuntu1.2",
"0.7-3.1ubuntu1.3",
"0.7-3.1ubuntu1.3+esm1",
"0.7-3.1ubuntu1.3+esm2",
"0.7-3.1ubuntu1.3+esm3",
"0.7-3.1ubuntu1.3+esm4"
]
}
],
"aliases": [],
"details": "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.",
"id": "UBUNTU-CVE-2021-26720",
"modified": "2026-05-20T14:53:11Z",
"published": "2021-02-17T22:15:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2021-26720"
},
{
"type": "REPORT",
"url": "https://www.openwall.com/lists/oss-security/2021/02/15/2"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2021-26720"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "low",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2021-26720"
]
}
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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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