UBUNTU-CVE-2026-102271 (CVE-2026-102271)
Vulnerability from osv_ubuntu – Published: 2026-09-28 21:17 – Updated: 2026-09-30 21:41 – Source website
VLAI
Details
PyJWT is a Python implementation of JSON Web Token standards. From 2.4.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because asymmetric-key guard relies on textual markers that are absent from DER encoding. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a DER public key as the shared verification key. As a result, PyJWT uses public DER bytes as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. This issue is fixed in version 2.14.0.
Severity
7.4 (High)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python-jwt",
"binary_version": "1.3.0-1ubuntu0.1+esm2"
},
{
"binary_name": "python3-jwt",
"binary_version": "1.3.0-1ubuntu0.1+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:16.04:LTS",
"name": "pyjwt",
"purl": "pkg:deb/ubuntu/pyjwt@1.3.0-1ubuntu0.1+esm2?arch=source\u0026distro=esm-infra-legacy/xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.0.0-0ubuntu1",
"1.3.0-1",
"1.3.0-1ubuntu0.1",
"1.3.0-1ubuntu0.1+esm1",
"1.3.0-1ubuntu0.1+esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python-jwt",
"binary_version": "1.5.3+ds1-1ubuntu0.1+esm2"
},
{
"binary_name": "python3-jwt",
"binary_version": "1.5.3+ds1-1ubuntu0.1+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:18.04:LTS",
"name": "pyjwt",
"purl": "pkg:deb/ubuntu/pyjwt@1.5.3+ds1-1ubuntu0.1+esm2?arch=source\u0026distro=esm-infra/bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.4.2-1.1",
"1.5.3+ds1-1",
"1.5.3+ds1-1ubuntu0.1",
"1.5.3+ds1-1ubuntu0.1+esm1",
"1.5.3+ds1-1ubuntu0.1+esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-jwt",
"binary_version": "1.7.1-2ubuntu2.1+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:20.04:LTS",
"name": "pyjwt",
"purl": "pkg:deb/ubuntu/pyjwt@1.7.1-2ubuntu2.1+esm2?arch=source\u0026distro=esm-infra/focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.7.0-2",
"1.7.1-1",
"1.7.1-2ubuntu1",
"1.7.1-2ubuntu2",
"1.7.1-2ubuntu2.1",
"1.7.1-2ubuntu2.1+esm1",
"1.7.1-2ubuntu2.1+esm2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-jwt",
"binary_version": "2.3.0-1ubuntu0.4"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "pyjwt",
"purl": "pkg:deb/ubuntu/pyjwt@2.3.0-1ubuntu0.4?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"1.7.1-2ubuntu2",
"2.1.0-1",
"2.3.0-1",
"2.3.0-1ubuntu0.1",
"2.3.0-1ubuntu0.2",
"2.3.0-1ubuntu0.3",
"2.3.0-1ubuntu0.4"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-jwt",
"binary_version": "2.7.0-1ubuntu0.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "pyjwt",
"purl": "pkg:deb/ubuntu/pyjwt@2.7.0-1ubuntu0.2?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.7.0-1",
"2.7.0-1ubuntu0.1",
"2.7.0-1ubuntu0.2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "python3-jwt",
"binary_version": "2.10.1-4ubuntu1.1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "pyjwt",
"purl": "pkg:deb/ubuntu/pyjwt@2.10.1-4ubuntu1.1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.10.1-2",
"2.10.1-3",
"2.10.1-3build1",
"2.10.1-4",
"2.10.1-4ubuntu1",
"2.10.1-4ubuntu1.1"
]
}
],
"aliases": [],
"details": "PyJWT is a Python implementation of JSON Web Token standards. From 2.4.0 until 2.14.0, PyJWT HMACAlgorithm.prepare_key is affected because asymmetric-key guard relies on textual markers that are absent from DER encoding. This occurs when an application mixes HMAC and asymmetric algorithms and supplies a DER public key as the shared verification key. As a result, PyJWT uses public DER bytes as an HMAC secret. Consequently, an attacker who knows the public key can forge authenticated HMAC tokens. This issue is fixed in version 2.14.0.",
"id": "UBUNTU-CVE-2026-102271",
"modified": "2026-09-30T21:41:54Z",
"published": "2026-09-28T21:17:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-102271"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-102271"
},
{
"type": "REPORT",
"url": "https://github.com/jpadilla/pyjwt/security/advisories/GHSA-p4g4-x82p-q773"
},
{
"type": "REPORT",
"url": "https://github.com/jpadilla/pyjwt/commit/2798504fa2663364573cf2d1043d8d7fef389499"
},
{
"type": "REPORT",
"url": "https://github.com/jpadilla/pyjwt/releases/tag/2.14.0"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-102271"
]
}
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Sightings
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Nomenclature
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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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