USN-4966-2 (UBUNTU-CVE-2021-31535)
Vulnerability from osv_ubuntu – Published: 2021-05-25 19:02 – Updated: 2026-06-29 10:52 – Source website
VLAI
Summary
libx11 vulnerability
Details
USN-4966-1 fixed a vulnerability in libx11. This update provides the corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.
Original advisory details:
It was discovered that libx11 incorrectly validated certain parameter lengths. A remote attacker could possibly use this issue to trick libx11 into emitting extra X protocol requests.
References
| URL | Type | |
|---|---|---|
{
"affected": [
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2021-31535",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:Pro:14.04:LTS"
}
},
"ecosystem_specific": {
"availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
"binaries": [
{
"binary_name": "libx11-6",
"binary_version": "2:1.6.2-1ubuntu2.1+esm2"
},
{
"binary_name": "libx11-data",
"binary_version": "2:1.6.2-1ubuntu2.1+esm2"
},
{
"binary_name": "libx11-xcb1",
"binary_version": "2:1.6.2-1ubuntu2.1+esm2"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:14.04:LTS",
"name": "libx11",
"purl": "pkg:deb/ubuntu/libx11@2:1.6.2-1ubuntu2.1+esm2?arch=source\u0026distro=trusty/esm"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2:1.6.2-1ubuntu2.1+esm2"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2:1.6.1-1ubuntu1",
"2:1.6.1-1ubuntu2",
"2:1.6.2-1ubuntu1",
"2:1.6.2-1ubuntu2",
"2:1.6.2-1ubuntu2.1",
"2:1.6.2-1ubuntu2.1+esm1"
]
},
{
"database_specific": {
"cves_map": {
"cves": [
{
"id": "CVE-2021-31535",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
]
}
],
"ecosystem": "Ubuntu:Pro:16.04:LTS"
}
},
"ecosystem_specific": {
"availability": "Available with Ubuntu Pro (Infra-only): https://ubuntu.com/pro",
"binaries": [
{
"binary_name": "libx11-6",
"binary_version": "2:1.6.3-1ubuntu2.2+esm1"
},
{
"binary_name": "libx11-data",
"binary_version": "2:1.6.3-1ubuntu2.2+esm1"
},
{
"binary_name": "libx11-xcb1",
"binary_version": "2:1.6.3-1ubuntu2.2+esm1"
}
]
},
"package": {
"ecosystem": "Ubuntu:Pro:16.04:LTS",
"name": "libx11",
"purl": "pkg:deb/ubuntu/libx11@2:1.6.3-1ubuntu2.2+esm1?arch=source\u0026distro=esm-infra/xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2:1.6.3-1ubuntu2.2+esm1"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2:1.6.3-1ubuntu2",
"2:1.6.3-1ubuntu2.1",
"2:1.6.3-1ubuntu2.2"
]
}
],
"aliases": [],
"details": "USN-4966-1 fixed a vulnerability in libx11. This update provides\nthe corresponding update for Ubuntu 14.04 ESM and Ubuntu 16.04 ESM.\n\nOriginal advisory details:\n\n It was discovered that libx11 incorrectly validated certain parameter\n lengths. A remote attacker could possibly use this issue to trick libx11\n into emitting extra X protocol requests.\n",
"id": "USN-4966-2",
"modified": "2026-06-29T10:52:50Z",
"published": "2021-05-25T19:02:59Z",
"references": [
{
"type": "ADVISORY",
"url": "https://ubuntu.com/security/notices/USN-4966-2"
},
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2021-31535"
}
],
"related": [],
"schema_version": "1.7.0",
"summary": "libx11 vulnerability",
"upstream": [
"UBUNTU-CVE-2021-31535"
]
}
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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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