UBUNTU-CVE-2026-63435 (CVE-2026-63435)
Vulnerability from osv_ubuntu – Published: 2026-09-01 21:18 – Updated: 2026-09-16 11:36 – Source website
VLAI
Details
Mail is an internet library for Ruby designed to handle email generation, parsing, and sending. Prior to 2.9.1, Mail::Utilities.q_value_decode and Mail::Utilities.b_value_decode used a single String#match and an overly greedy charset capture to decode only the first RFC 2047 encoded-word and mishandle surrounding or subsequent text. A crafted malformed encoded-word in an address display name or local part could cross ? delimiters and make decoded From, To, or Reply-To header values differ from the raw values inspected by a human reviewer or downstream parser, enabling apparent sender or recipient spoofing, phishing, or authorization-check bypass. This issue is fixed in version 2.9.1.
Severity
5.3 (Medium)
N/A (UNKNOWN)
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "jruby",
"binary_version": "1.5.6-9+deb8u2build0.14.04.1~esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:14.04:LTS",
"name": "jruby",
"purl": "pkg:deb/ubuntu/jruby@1.5.6-9+deb8u2build0.14.04.1~esm2?arch=source\u0026distro=esm-infra-legacy/trusty"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.5.6-5ubuntu1",
"1.5.6-6",
"1.5.6-7",
"1.5.6-9+deb8u2build0.14.04.1~esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libruby2.3",
"binary_version": "2.3.1-2~ubuntu16.04.16+esm15"
},
{
"binary_name": "ruby2.3",
"binary_version": "2.3.1-2~ubuntu16.04.16+esm15"
},
{
"binary_name": "ruby2.3-tcltk",
"binary_version": "2.3.1-2~ubuntu16.04.16+esm15"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:16.04:LTS",
"name": "ruby2.3",
"purl": "pkg:deb/ubuntu/ruby2.3@2.3.1-2~ubuntu16.04.16+esm15?arch=source\u0026distro=esm-infra-legacy/xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.3.0-1",
"2.3.0-2",
"2.3.0-4ubuntu2",
"2.3.0-4ubuntu3",
"2.3.0-5ubuntu1",
"2.3.1-2~16.04",
"2.3.1-2~16.04.2",
"2.3.1-2~16.04.4",
"2.3.1-2~16.04.5",
"2.3.1-2~16.04.6",
"2.3.1-2~16.04.7",
"2.3.1-2~16.04.9",
"2.3.1-2~16.04.10",
"2.3.1-2~16.04.11",
"2.3.1-2~16.04.12",
"2.3.1-2~ubuntu16.04.13",
"2.3.1-2~ubuntu16.04.14",
"2.3.1-2~ubuntu16.04.15",
"2.3.1-2~ubuntu16.04.16",
"2.3.1-2~ubuntu16.04.16+esm1",
"2.3.1-2~ubuntu16.04.16+esm2",
"2.3.1-2~ubuntu16.04.16+esm3",
"2.3.1-2~ubuntu16.04.16+esm4",
"2.3.1-2~ubuntu16.04.16+esm5",
"2.3.1-2~ubuntu16.04.16+esm6",
"2.3.1-2~ubuntu16.04.16+esm7",
"2.3.1-2~ubuntu16.04.16+esm8",
"2.3.1-2~ubuntu16.04.16+esm9",
"2.3.1-2~ubuntu16.04.16+esm10",
"2.3.1-2~ubuntu16.04.16+esm11",
"2.3.1-2~ubuntu16.04.16+esm12",
"2.3.1-2~ubuntu16.04.16+esm14",
"2.3.1-2~ubuntu16.04.16+esm15"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "jruby",
"binary_version": "1.7.22-1ubuntu1"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "jruby",
"purl": "pkg:deb/ubuntu/jruby@1.7.22-1ubuntu1?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.7.21-2ubuntu4",
"1.7.22-1ubuntu1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libruby2.5",
"binary_version": "2.5.1-1ubuntu1.16+esm8"
},
{
"binary_name": "ruby2.5",
"binary_version": "2.5.1-1ubuntu1.16+esm8"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:18.04:LTS",
"name": "ruby2.5",
"purl": "pkg:deb/ubuntu/ruby2.5@2.5.1-1ubuntu1.16+esm8?arch=source\u0026distro=esm-infra/bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.5.0~preview1-1ubuntu2",
"2.5.0-4ubuntu1",
"2.5.0-4ubuntu4",
"2.5.0-5ubuntu1",
"2.5.0-6ubuntu1",
"2.5.1-1ubuntu1",
"2.5.1-1ubuntu1.1",
"2.5.1-1ubuntu1.2",
"2.5.1-1ubuntu1.4",
"2.5.1-1ubuntu1.5",
"2.5.1-1ubuntu1.6",
"2.5.1-1ubuntu1.7",
"2.5.1-1ubuntu1.8",
"2.5.1-1ubuntu1.9",
"2.5.1-1ubuntu1.10",
"2.5.1-1ubuntu1.11",
"2.5.1-1ubuntu1.12",
"2.5.1-1ubuntu1.13",
"2.5.1-1ubuntu1.14",
"2.5.1-1ubuntu1.15",
"2.5.1-1ubuntu1.16",
"2.5.1-1ubuntu1.16+esm1",
"2.5.1-1ubuntu1.16+esm3",
"2.5.1-1ubuntu1.16+esm4",
"2.5.1-1ubuntu1.16+esm5",
"2.5.1-1ubuntu1.16+esm6",
"2.5.1-1ubuntu1.16+esm7",
"2.5.1-1ubuntu1.16+esm8"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "jruby",
"binary_version": "9.1.17.0-1~18.04"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "jruby",
"purl": "pkg:deb/ubuntu/jruby@9.1.17.0-1~18.04?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"9.1.13.0-1",
"9.1.17.0-1~18.04"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libruby2.7",
"binary_version": "2.7.0-5ubuntu1.18+esm5"
},
{
"binary_name": "ruby2.7",
"binary_version": "2.7.0-5ubuntu1.18+esm5"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:20.04:LTS",
"name": "ruby2.7",
"purl": "pkg:deb/ubuntu/ruby2.7@2.7.0-5ubuntu1.18+esm5?arch=source\u0026distro=esm-infra/focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.7.0-1",
"2.7.0-2",
"2.7.0-3",
"2.7.0-4",
"2.7.0-4ubuntu1",
"2.7.0-5ubuntu1",
"2.7.0-5ubuntu1.1",
"2.7.0-5ubuntu1.2",
"2.7.0-5ubuntu1.3",
"2.7.0-5ubuntu1.4",
"2.7.0-5ubuntu1.5",
"2.7.0-5ubuntu1.6",
"2.7.0-5ubuntu1.7",
"2.7.0-5ubuntu1.8",
"2.7.0-5ubuntu1.9",
"2.7.0-5ubuntu1.10",
"2.7.0-5ubuntu1.11",
"2.7.0-5ubuntu1.12",
"2.7.0-5ubuntu1.13",
"2.7.0-5ubuntu1.14",
"2.7.0-5ubuntu1.15",
"2.7.0-5ubuntu1.16",
"2.7.0-5ubuntu1.17",
"2.7.0-5ubuntu1.18",
"2.7.0-5ubuntu1.18+esm1",
"2.7.0-5ubuntu1.18+esm3",
"2.7.0-5ubuntu1.18+esm4",
"2.7.0-5ubuntu1.18+esm5"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "jruby",
"binary_version": "9.1.17.0-3build6"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "jruby",
"purl": "pkg:deb/ubuntu/jruby@9.1.17.0-3build6?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"9.1.17.0-3",
"9.1.17.0-3build5",
"9.1.17.0-3build6"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libruby3.0",
"binary_version": "3.0.2-7ubuntu2.13"
},
{
"binary_name": "ruby3.0",
"binary_version": "3.0.2-7ubuntu2.13"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "ruby3.0",
"purl": "pkg:deb/ubuntu/ruby3.0@3.0.2-7ubuntu2.13?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"3.0.2-5ubuntu1",
"3.0.2-7",
"3.0.2-7ubuntu2",
"3.0.2-7ubuntu2.1",
"3.0.2-7ubuntu2.2",
"3.0.2-7ubuntu2.3",
"3.0.2-7ubuntu2.4",
"3.0.2-7ubuntu2.5",
"3.0.2-7ubuntu2.6",
"3.0.2-7ubuntu2.7",
"3.0.2-7ubuntu2.8",
"3.0.2-7ubuntu2.10",
"3.0.2-7ubuntu2.11",
"3.0.2-7ubuntu2.12",
"3.0.2-7ubuntu2.13"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "jruby",
"binary_version": "9.4.6.0+ds-1ubuntu3"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "jruby",
"purl": "pkg:deb/ubuntu/jruby@9.4.6.0+ds-1ubuntu3?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"9.3.9.0+ds-1",
"9.4.5.0+ds-1",
"9.4.5.0+ds-1ubuntu1",
"9.4.6.0+ds-1ubuntu3"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libruby3.2",
"binary_version": "3.2.3-1ubuntu0.24.04.8"
},
{
"binary_name": "ruby3.2",
"binary_version": "3.2.3-1ubuntu0.24.04.8"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "ruby3.2",
"purl": "pkg:deb/ubuntu/ruby3.2@3.2.3-1ubuntu0.24.04.8?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"3.2.3-1",
"3.2.3-1build2",
"3.2.3-1build3",
"3.2.3-1ubuntu0.24.04.1",
"3.2.3-1ubuntu0.24.04.3",
"3.2.3-1ubuntu0.24.04.5",
"3.2.3-1ubuntu0.24.04.6",
"3.2.3-1ubuntu0.24.04.7",
"3.2.3-1ubuntu0.24.04.8"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "jruby",
"binary_version": "9.4.8.0+ds-3ubuntu1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "jruby",
"purl": "pkg:deb/ubuntu/jruby@9.4.8.0+ds-3ubuntu1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"9.4.8.0+ds-3ubuntu1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libruby3.3",
"binary_version": "3.3.8-2ubuntu3.1"
},
{
"binary_name": "ruby3.3",
"binary_version": "3.3.8-2ubuntu3.1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "ruby3.3",
"purl": "pkg:deb/ubuntu/ruby3.3@3.3.8-2ubuntu3.1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"3.3.8-2ubuntu2",
"3.3.8-2ubuntu3",
"3.3.8-2ubuntu3.1"
]
}
],
"aliases": [],
"details": "Mail is an internet library for Ruby designed to handle email generation, parsing, and sending. Prior to 2.9.1, Mail::Utilities.q_value_decode and Mail::Utilities.b_value_decode used a single String#match and an overly greedy charset capture to decode only the first RFC 2047 encoded-word and mishandle surrounding or subsequent text. A crafted malformed encoded-word in an address display name or local part could cross ? delimiters and make decoded From, To, or Reply-To header values differ from the raw values inspected by a human reviewer or downstream parser, enabling apparent sender or recipient spoofing, phishing, or authorization-check bypass. This issue is fixed in version 2.9.1.",
"id": "UBUNTU-CVE-2026-63435",
"modified": "2026-09-16T11:36:44Z",
"published": "2026-09-01T21:18:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-63435"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-63435"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-63435"
]
}
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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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