UBUNTU-CVE-2021-22903 (CVE-2021-22903)
Vulnerability from osv_ubuntu – Published: 2021-06-11 16:15 – Updated: 2026-05-20 14:53 – Source website
VLAI
Details
The actionpack ruby gem before 6.1.3.2 suffers from a possible open redirect vulnerability. Specially crafted Host headers in combination with certain "allowed host" formats can cause the Host Authorization middleware in Action Pack to redirect users to a malicious website. This is similar to CVE-2021-22881. Strings in config.hosts that do not have a leading dot are converted to regular expressions without proper escaping. This causes, for example, config.hosts << "sub.example.com" to permit a request with a Host header value of sub-example.com.
Severity
6.1 (Medium)
N/A (UNKNOWN)
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "rails",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
},
{
"binary_name": "ruby-actionmailer",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
},
{
"binary_name": "ruby-actionpack",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
},
{
"binary_name": "ruby-actionview",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
},
{
"binary_name": "ruby-activejob",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
},
{
"binary_name": "ruby-activemodel",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
},
{
"binary_name": "ruby-activerecord",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
},
{
"binary_name": "ruby-activesupport",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
},
{
"binary_name": "ruby-rails",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
},
{
"binary_name": "ruby-railties",
"binary_version": "2:4.2.6-1ubuntu0.1~esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:16.04:LTS",
"name": "rails",
"purl": "pkg:deb/ubuntu/rails@2:4.2.6-1ubuntu0.1~esm2?arch=source\u0026distro=esm-apps/xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2:4.1.10-1",
"2:4.2.5-1",
"2:4.2.5.1-1",
"2:4.2.5.2-2",
"2:4.2.6-1",
"2:4.2.6-1ubuntu0.1~esm1",
"2:4.2.6-1ubuntu0.1~esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "rails",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
},
{
"binary_name": "ruby-actionmailer",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
},
{
"binary_name": "ruby-actionpack",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
},
{
"binary_name": "ruby-actionview",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
},
{
"binary_name": "ruby-activejob",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
},
{
"binary_name": "ruby-activemodel",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
},
{
"binary_name": "ruby-activerecord",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
},
{
"binary_name": "ruby-activesupport",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
},
{
"binary_name": "ruby-rails",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
},
{
"binary_name": "ruby-railties",
"binary_version": "2:4.2.10-0ubuntu4+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:18.04:LTS",
"name": "rails",
"purl": "pkg:deb/ubuntu/rails@2:4.2.10-0ubuntu4+esm2?arch=source\u0026distro=esm-apps/bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2:4.2.9-2",
"2:4.2.9-4",
"2:4.2.10-0ubuntu4",
"2:4.2.10-0ubuntu4+esm1",
"2:4.2.10-0ubuntu4+esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "rails",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-actioncable",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-actionmailer",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-actionpack",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-actionview",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-activejob",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-activemodel",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-activerecord",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-activestorage",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-activesupport",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-rails",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
},
{
"binary_name": "ruby-railties",
"binary_version": "2:5.2.3+dfsg-3ubuntu0.1~esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:20.04:LTS",
"name": "rails",
"purl": "pkg:deb/ubuntu/rails@2:5.2.3+dfsg-3ubuntu0.1~esm1?arch=source\u0026distro=esm-apps/focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2:5.2.2.1+dfsg-1ubuntu1",
"2:5.2.3+dfsg-3",
"2:5.2.3+dfsg-3ubuntu0.1~esm1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "rails",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-actioncable",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-actionmailbox",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-actionmailer",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-actionpack",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-actiontext",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-actionview",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-activejob",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-activemodel",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-activerecord",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-activestorage",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-activesupport",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-rails",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
},
{
"binary_name": "ruby-railties",
"binary_version": "2:6.1.4.1+dfsg-8ubuntu2+esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:22.04:LTS",
"name": "rails",
"purl": "pkg:deb/ubuntu/rails@2:6.1.4.1+dfsg-8ubuntu2+esm1?arch=source\u0026distro=esm-apps/jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2:6.0.3.7+dfsg-2",
"2:6.1.4.1+dfsg-8ubuntu2",
"2:6.1.4.1+dfsg-8ubuntu2+esm1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "rails",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-actioncable",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-actionmailbox",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-actionmailer",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-actionpack",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-actiontext",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-actionview",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-activejob",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-activemodel",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-activerecord",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-activestorage",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-activesupport",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-rails",
"binary_version": "2:6.1.7.3+dfsg-3"
},
{
"binary_name": "ruby-railties",
"binary_version": "2:6.1.7.3+dfsg-3"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "rails",
"purl": "pkg:deb/ubuntu/rails@2:6.1.7.3+dfsg-3?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2:6.1.7.3+dfsg-2build1",
"2:6.1.7.3+dfsg-3"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "rails",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-actioncable",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-actionmailbox",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-actionmailer",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-actionpack",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-actiontext",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-actionview",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-activejob",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-activemodel",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-activerecord",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-activestorage",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-activesupport",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-rails",
"binary_version": "2:7.2.2.1+dfsg-7"
},
{
"binary_name": "ruby-railties",
"binary_version": "2:7.2.2.1+dfsg-7"
}
]
},
"package": {
"ecosystem": "Ubuntu:25.10",
"name": "rails",
"purl": "pkg:deb/ubuntu/rails@2:7.2.2.1+dfsg-7?arch=source\u0026distro=questing"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2:6.1.7.3+dfsg-7",
"2:7.2.2.1+dfsg-7"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "rails",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-actioncable",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-actionmailbox",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-actionmailer",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-actionpack",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-actiontext",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-actionview",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-activejob",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-activemodel",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-activerecord",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-activestorage",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-activesupport",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-rails",
"binary_version": "2:7.2.3+dfsg-2"
},
{
"binary_name": "ruby-railties",
"binary_version": "2:7.2.3+dfsg-2"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "rails",
"purl": "pkg:deb/ubuntu/rails@2:7.2.3+dfsg-2?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2:7.2.2.1+dfsg-7",
"2:7.2.2.2+dfsg-2",
"2:7.2.3+dfsg-2"
]
}
],
"aliases": [],
"details": "The actionpack ruby gem before 6.1.3.2 suffers from a possible open redirect vulnerability. Specially crafted Host headers in combination with certain \"allowed host\" formats can cause the Host Authorization middleware in Action Pack to redirect users to a malicious website. This is similar to CVE-2021-22881. Strings in config.hosts that do not have a leading dot are converted to regular expressions without proper escaping. This causes, for example, `config.hosts \u003c\u003c \"sub.example.com\"` to permit a request with a Host header value of `sub-example.com`.",
"id": "UBUNTU-CVE-2021-22903",
"modified": "2026-05-20T14:53:08Z",
"published": "2021-06-11T16:15:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2021-22903"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2021-22903"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2021-22903"
]
}
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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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